diff --git a/packages/accounts-ui-unstyled/login_buttons.less b/packages/accounts-ui-unstyled/login_buttons.import.less
similarity index 100%
rename from packages/accounts-ui-unstyled/login_buttons.less
rename to packages/accounts-ui-unstyled/login_buttons.import.less
diff --git a/packages/accounts-ui-unstyled/package.js b/packages/accounts-ui-unstyled/package.js
index 9311fd6928..d2556b11ca 100644
--- a/packages/accounts-ui-unstyled/package.js
+++ b/packages/accounts-ui-unstyled/package.js
@@ -33,10 +33,10 @@ Package.onUse(function (api) {
 
   // The less source defining the default style for accounts-ui. Just adding
   // this package doesn't actually apply these styles; they need to be
-  // `@import`ed from some *.main.less file.  The accounts-ui package does that
-  // for you, or you can do it in your app.
+  // `@import`ed from some non-import less file.  The accounts-ui package does
+  // that for you, or you can do it in your app.
   api.use('less');
-  api.addFiles('login_buttons.less');
+  api.addFiles('login_buttons.import.less');
 });
 
 Package.onTest(function (api) {
diff --git a/packages/accounts-ui/login_buttons.main.less b/packages/accounts-ui/login_buttons.less
similarity index 100%
rename from packages/accounts-ui/login_buttons.main.less
rename to packages/accounts-ui/login_buttons.less
diff --git a/packages/accounts-ui/package.js b/packages/accounts-ui/package.js
index 9dc4cd09ac..91a0dbcf14 100644
--- a/packages/accounts-ui/package.js
+++ b/packages/accounts-ui/package.js
@@ -9,5 +9,5 @@ Package.onUse(function (api) {
   api.use('accounts-ui-unstyled', 'client');
   api.use('less', 'client');
 
-  api.addFiles(['login_buttons.main.less'], 'client');
+  api.addFiles(['login_buttons.less'], 'client');
 });
diff --git a/packages/less/package.js b/packages/less/package.js
index cc241f05bd..491e0cf293 100644
--- a/packages/less/package.js
+++ b/packages/less/package.js
@@ -25,13 +25,14 @@ Package.onUse(function (api) {
 Package.onTest(function(api) {
   api.use('less');
   api.use(['tinytest', 'test-helpers']);
-  api.addFiles(['tests/top.less',
-                'tests/top2.less',
-                'tests/top3.less',
-                'tests/not-included.less',
-                'tests/dir/in-dir.less',
-                'tests/dir/in-dir2.less',
-                'tests/dir/root.main.less',
-                'tests/dir/subdir/in-subdir.less']);
+  api.addFiles(['tests/top.import.less',
+                'tests/top3.import.less',
+                'tests/import/not-included.less',
+                'tests/dir/in-dir.import.less',
+                'tests/dir/in-dir2.import.less',
+                'tests/dir/root.less',
+                'tests/dir/subdir/in-subdir.import.less']);
+  api.addFiles('tests/top2.less', 'client', {isImport: true});
+
   api.addFiles('less_tests.js', 'client');
 });
diff --git a/packages/less/plugin/compile-less.js b/packages/less/plugin/compile-less.js
index 73c2321d8d..d4ec8cb0b8 100644
--- a/packages/less/plugin/compile-less.js
+++ b/packages/less/plugin/compile-less.js
@@ -6,7 +6,9 @@ var Future = Npm.require('fibers/future');
 var LRU = Npm.require('lru-cache');
 
 Plugin.registerCompiler({
-  extensions: ['less'],
+  // *.lessimport has been deprecated since 0.7.1, but it still works. We
+  // *recommend *.import.less or the import subdirectory instead.
+  extensions: ['less', 'lessimport'],
   archMatching: 'web'
 }, function () {
     return new LessCompiler();
@@ -35,7 +37,7 @@ _.extend(LessCompiler.prototype, {
   processFilesForTarget: function (inputFiles) {
     var self = this;
     var filesByAbsoluteImportPath = {};
-    var mains = [];
+    var roots = [];
     var cacheMisses = [];
 
     function decodeFilePath (filePath) {
@@ -54,20 +56,32 @@ _.extend(LessCompiler.prototype, {
     inputFiles.forEach(function (inputFile) {
       var packageName = inputFile.getPackageName();
       var pathInPackage = inputFile.getPathInPackage();
+      var fileOptions = inputFile.getFileOptions();
       var absoluteImportPath = packageName === null
             ? ('{}/' + pathInPackage)
             : ('{' + packageName + '}/' + pathInPackage);
       filesByAbsoluteImportPath[absoluteImportPath] = inputFile;
+
+      // The heuristic is that a file is an import (ie, is not itself processed
+      // as a root) if it is in a subdirectory named 'import' or if it matches
+      // *.import.less. This can be overridden in either direction via an
+      // explicit `isImport` file option in apiaddFiles.
+      var filenameSaysImport =
+            /\.import\.less$/.test(pathInPackage) ||
+            /\.lessimport$/.test(pathInPackage) ||
+            /(?:^|\/)import\//.test(pathInPackage);
+      var isImport = fileOptions.hasOwnProperty('isImport')
+            ? fileOptions.isImport : filenameSaysImport;
       // Match files named `main.less` or with a `.main.less` extension
-      if (pathInPackage.match(/(^|\/|\.)main\.less$/)) {
-        mains.push({inputFile: inputFile,
+      if (! isImport) {
+        roots.push({inputFile: inputFile,
                     absoluteImportPath: absoluteImportPath});
       }
     });
 
     var importPlugin = new MeteorImportLessPlugin(filesByAbsoluteImportPath);
 
-    mains.forEach(function (main) {
+    roots.forEach(function (main) {
       var inputFile = main.inputFile;
       var absoluteImportPath = main.absoluteImportPath;
 
diff --git a/packages/less/tests/dir/in-dir.less b/packages/less/tests/dir/in-dir.import.less
similarity index 100%
rename from packages/less/tests/dir/in-dir.less
rename to packages/less/tests/dir/in-dir.import.less
diff --git a/packages/less/tests/dir/in-dir2.less b/packages/less/tests/dir/in-dir2.import.less
similarity index 100%
rename from packages/less/tests/dir/in-dir2.less
rename to packages/less/tests/dir/in-dir2.import.less
diff --git a/packages/less/tests/dir/root.main.less b/packages/less/tests/dir/root.less
similarity index 65%
rename from packages/less/tests/dir/root.main.less
rename to packages/less/tests/dir/root.less
index 809f28eaba..192beba072 100644
--- a/packages/less/tests/dir/root.main.less
+++ b/packages/less/tests/dir/root.less
@@ -1,8 +1,8 @@
-@import "/tests/top.less";
+@import "/tests/top.import.less";
 @import "{local-test:less}/tests/top2.less";
-@import "in-dir.less";
-@import "./in-dir2.less";
-@import "subdir/in-subdir.less";
+@import "in-dir.import.less";
+@import "./in-dir2.import.less";
+@import "subdir/in-subdir.import.less";
 
 
 .el1 { border-style: @el1-style; }
diff --git a/packages/less/tests/dir/subdir/in-subdir.less b/packages/less/tests/dir/subdir/in-subdir.import.less
similarity index 100%
rename from packages/less/tests/dir/subdir/in-subdir.less
rename to packages/less/tests/dir/subdir/in-subdir.import.less
diff --git a/packages/less/tests/not-included.less b/packages/less/tests/import/not-included.less
similarity index 100%
rename from packages/less/tests/not-included.less
rename to packages/less/tests/import/not-included.less
diff --git a/packages/less/tests/top.less b/packages/less/tests/top.import.less
similarity index 76%
rename from packages/less/tests/top.less
rename to packages/less/tests/top.import.less
index 1f80ae5349..4d9828eecd 100644
--- a/packages/less/tests/top.less
+++ b/packages/less/tests/top.import.less
@@ -2,4 +2,4 @@
 
 /* Test that package-relative imports work from within a
  * package-relative-imported file */
-@import "/tests/top3.less";
+@import "/tests/top3.import.less";
diff --git a/packages/less/tests/top3.less b/packages/less/tests/top3.import.less
similarity index 100%
rename from packages/less/tests/top3.less
rename to packages/less/tests/top3.import.less
diff --git a/tools/compiler-plugin.js b/tools/compiler-plugin.js
index ebfca06fc2..f0f16ff7fd 100644
--- a/tools/compiler-plugin.js
+++ b/tools/compiler-plugin.js
@@ -134,7 +134,7 @@ _.extend(InputFile.prototype, {
     var self = this;
     // XXX fileOptions only exists on some resources (of type "source"). The JS
     // resources might not have this property.
-    return self._resourceSlot.inputResource.fileOptions;
+    return self._resourceSlot.inputResource.fileOptions || {};
   },
   getArch: function () {
     return this._resourceSlot.packageSourceBatch.processor.arch;
diff --git a/tools/tests/apps/coffee-and-less/dotdot.less b/tools/tests/apps/coffee-and-less/import/dotdot.less
similarity index 100%
rename from tools/tests/apps/coffee-and-less/dotdot.less
rename to tools/tests/apps/coffee-and-less/import/dotdot.less
diff --git a/tools/tests/apps/coffee-and-less/packages/local-pack/package.js b/tools/tests/apps/coffee-and-less/packages/local-pack/package.js
index 3574e4e155..4f0df7b7b1 100644
--- a/tools/tests/apps/coffee-and-less/packages/local-pack/package.js
+++ b/tools/tests/apps/coffee-and-less/packages/local-pack/package.js
@@ -1,5 +1,6 @@
 Package.onUse(function (api) {
   api.use(['coffeescript', 'less']);
-  api.addFiles(['p.coffee', 'p.less']);
+  api.addFiles(['p.coffee']);
+  api.addFiles('p.less', 'client', {isImport: true});
   api.export('FromPackage');
 });
diff --git a/tools/tests/apps/coffee-and-less/subdir/foo.import.less b/tools/tests/apps/coffee-and-less/subdir/foo.import.less
new file mode 100644
index 0000000000..c3505dfd93
--- /dev/null
+++ b/tools/tests/apps/coffee-and-less/subdir/foo.import.less
@@ -0,0 +1,2 @@
+@el2-style: solid;
+@import "../import/dotdot.less";
diff --git a/tools/tests/apps/coffee-and-less/subdir/foo.less b/tools/tests/apps/coffee-and-less/subdir/foo.less
deleted file mode 100644
index 2261e8cc30..0000000000
--- a/tools/tests/apps/coffee-and-less/subdir/foo.less
+++ /dev/null
@@ -1,2 +0,0 @@
-@el2-style: solid;
-@import "../dotdot.less";
diff --git a/tools/tests/apps/coffee-and-less/subdir/nested-root.main.less b/tools/tests/apps/coffee-and-less/subdir/nested-root.less
similarity index 100%
rename from tools/tests/apps/coffee-and-less/subdir/nested-root.main.less
rename to tools/tests/apps/coffee-and-less/subdir/nested-root.less
diff --git a/tools/tests/apps/coffee-and-less/top.main.less b/tools/tests/apps/coffee-and-less/top.less
similarity index 85%
rename from tools/tests/apps/coffee-and-less/top.main.less
rename to tools/tests/apps/coffee-and-less/top.less
index 3ce4459c9c..3d9f6da5a8 100644
--- a/tools/tests/apps/coffee-and-less/top.main.less
+++ b/tools/tests/apps/coffee-and-less/top.less
@@ -1,5 +1,5 @@
 @first-style: dotted;
-@import "subdir/foo.less";
+@import "subdir/foo.import.less";
 
 .el1 { border-style: @first-style; }
 .el2 { border-style: @el2-style; }
diff --git a/tools/tests/compiler-plugins.js b/tools/tests/compiler-plugins.js
index 6d58981ebe..ecc7c9a74e 100644
--- a/tools/tests/compiler-plugins.js
+++ b/tools/tests/compiler-plugins.js
@@ -34,7 +34,7 @@ selftest.define("compiler plugin caching - coffee/less", function () {
     ['/f1.coffee', '/f2.coffee', '/f3.coffee', '/packages/local-pack/p.coffee']
   ));
   run.match('Ran less.render (#1) on: ' + JSON.stringify(
-    ["/subdir/nested-root.main.less", "/top.main.less"]));
+    ["/subdir/nested-root.less", "/top.less"]));
   // Second program doesn't need to compile anything because compilation works
   // the same on both programs.  (Note that there is no less.render execution in
   // the second program, because it has archMatching: 'web'.  We'll see this
@@ -97,26 +97,26 @@ selftest.define("compiler plugin caching - coffee/less", function () {
   s.write('packages/local-pack/p.less', '@el4-style: inset;\n');
   expectedBorderStyles.el4 = 'inset';
   run.match('Ran coffee.compile (#9) on: []');
-  run.match('Ran less.render (#5) on: ["/top.main.less"]');
+  run.match('Ran less.render (#5) on: ["/top.less"]');
   // Note that since this was a client-only change, we're smart enough to not
   // rebuild the server at all.  So the next coffee.compile will be #10.
   run.match("Client modified -- refreshing");
   checkCSS(expectedBorderStyles);
 
   // This works for changing a root too.
-  s.write('subdir/nested-root.main.less', '.el0 { border-style: double; }\n');
+  s.write('subdir/nested-root.less', '.el0 { border-style: double; }\n');
   expectedBorderStyles.el0 = 'double';
   // Only #10, not #11, because client-only changes don't rebuild the server!
   run.match('Ran coffee.compile (#10) on: []');
-  run.match('Ran less.render (#6) on: ["/subdir/nested-root.main.less"]');
+  run.match('Ran less.render (#6) on: ["/subdir/nested-root.less"]');
   run.match("Client modified -- refreshing");
   checkCSS(expectedBorderStyles);
 
   // Adding a new root works too.
-  s.write('yet-another-root.main.less', '.el6 { border-style: solid; }\n');
+  s.write('yet-another-root.less', '.el6 { border-style: solid; }\n');
   expectedBorderStyles.el6 = 'solid';
   run.match('Ran coffee.compile (#11) on: []');
-  run.match('Ran less.render (#7) on: ["/yet-another-root.main.less"]');
+  run.match('Ran less.render (#7) on: ["/yet-another-root.less"]');
   run.match("Client modified -- refreshing");
   checkCSS(expectedBorderStyles);
 
@@ -137,15 +137,15 @@ selftest.define("compiler plugin caching - coffee/less", function () {
   run.match('Loaded less cache');
   // And we only need to re-compiler the changed file, even though we restarted.
   run.match('Ran coffee.compile (#1) on: ["/f2.coffee"]');
-  run.match('Ran less.render (#1) on: ["/top.main.less"]');
+  run.match('Ran less.render (#1) on: ["/top.less"]');
   run.match('Ran coffee.compile (#2) on: []');
 
   run.match('Coffeescript X is 2 Y is edited FromPackage is 5');
   checkCSS(expectedBorderStyles);
 
-  s.write('bad-import.main.less', '@import "/foo/bad.less";\n');
+  s.write('bad-import.less', '@import "/foo/bad.less";\n');
   run.match('Errors prevented startup');
-  run.match('bad-import.main.less:1: Unknown import: /foo/bad.less');
+  run.match('bad-import.less:1: Unknown import: /foo/bad.less');
   run.match('Waiting for file change');
 
   run.stop();
diff --git a/tools/upgraders.js b/tools/upgraders.js
index 41a1955f3a..9d8c0ddd2e 100644
--- a/tools/upgraders.js
+++ b/tools/upgraders.js
@@ -134,8 +134,6 @@ var upgradersByName = {
     projectContext.projectConstraintsFile.writeIfModified();
   }
 
-  // XXX #BBPLessUpgrader Write an upgrader explaining the changes to less.
-
   ////////////
   // PLEASE. When adding new upgraders that print mesasges, follow the
   // examples for 0.9.0 and 0.9.1 above. Specifically, formatting