diff --git a/spec/atom/highlighter-spec.coffee b/spec/atom/highlighter-spec.coffee
new file mode 100644
index 000000000..71f8fbaf8
--- /dev/null
+++ b/spec/atom/highlighter-spec.coffee
@@ -0,0 +1,71 @@
+Highlighter = require 'highlighter'
+Buffer = require 'buffer'
+Range = require 'range'
+
+describe "Highlighter", ->
+  [highlighter, buffer] = []
+
+  beforeEach ->
+    buffer = new Buffer(require.resolve('fixtures/sample.js'))
+    highlighter = new Highlighter(buffer)
+
+  describe "constructor", ->
+    it "tokenizes all the lines in the buffer", ->
+      expect(highlighter.tokensForRow(0)[0]).toEqual(type: 'keyword.definition', value: 'var')
+      expect(highlighter.tokensForRow(11)[1]).toEqual(type: 'keyword', value: 'return')
+
+  describe "when the buffer changes", ->
+    describe "when a single line is changed", ->
+      it "updates tokens for the changed line", ->
+        expect(highlighter.tokensForRow(0)[0]).toEqual(type: 'keyword.definition', value: 'var')
+        buffer.change(new Range([0, 0], [0, 4]), '')
+        expect(highlighter.tokensForRow(0)[0]).toEqual(type: 'identifier', value: 'quicksort')
+
+      it "preserves the scanning state when tokenizing the changed line"
+        # change the second line of a multi line comment and make sure it's still recognized as such
+
+    describe "when multiple lines are updated, but none are added or removed", ->
+      it "updates tokens for each of the changed lines", ->
+        buffer.change(new Range([0, 0], [2, 0]), "foo()\nbar()\n")
+
+        expect(highlighter.tokensForRow(0)[0]).toEqual(type: 'identifier', value: 'foo')
+        expect(highlighter.tokensForRow(1)[0]).toEqual(type: 'identifier', value: 'bar')
+
+        # line 2 is unchanged
+        expect(highlighter.tokensForRow(2)[1]).toEqual(type: 'keyword', value: 'if')
+
+    describe "when lines are both updated and removed", ->
+      it "updates tokens to reflect the removed lines", ->
+        buffer.change(new Range([1, 0], [3, 0]), "foo()")
+
+        # previous line 0 remains
+        expect(highlighter.tokensForRow(0)[0]).toEqual(type: 'keyword.definition', value: 'var')
+
+        # previous line 3 should be combined with input to form line 1
+        expect(highlighter.tokensForRow(1)[0]).toEqual(type: 'identifier', value: 'foo')
+        expect(highlighter.tokensForRow(1)[6]).toEqual(type: 'identifier', value: 'pivot')
+
+        # lines below deleted regions should be shifted upward
+        expect(highlighter.tokensForRow(2)[1]).toEqual(type: 'keyword', value: 'while')
+        expect(highlighter.tokensForRow(3)[1]).toEqual(type: 'identifier', value: 'current')
+        expect(highlighter.tokensForRow(4)[3]).toEqual(type: 'keyword.operator', value: '<')
+
+    describe "when lines are both updated and inserted", ->
+      it "updates tokens to reflect the inserted lines", ->
+        buffer.change(new Range([1, 0], [2, 0]), "foo()\nbar()\nbaz()\nquux()")
+
+        # previous line 0 remains
+        expect(highlighter.tokensForRow(0)[0]).toEqual(type: 'keyword.definition', value: 'var')
+
+        # 3 new lines inserted
+        expect(highlighter.tokensForRow(1)[0]).toEqual(type: 'identifier', value: 'foo')
+        expect(highlighter.tokensForRow(2)[0]).toEqual(type: 'identifier', value: 'bar')
+        expect(highlighter.tokensForRow(3)[0]).toEqual(type: 'identifier', value: 'baz')
+
+        # previous line 2 is joined with quux() on line 4
+        expect(highlighter.tokensForRow(4)[0]).toEqual(type: 'identifier', value: 'quux')
+        expect(highlighter.tokensForRow(4)[4]).toEqual(type: 'keyword', value: 'if')
+
+        # previous line 3 is pushed down to become line 5
+        expect(highlighter.tokensForRow(5)[3]).toEqual(type: 'identifier', value: 'pivot')
+
diff --git a/src/atom/editor.coffee b/src/atom/editor.coffee
index 920855283..0c79688b3 100644
--- a/src/atom/editor.coffee
+++ b/src/atom/editor.coffee
@@ -91,7 +91,7 @@ class Editor extends Template
         @focus()
 
     buildLineElement: (row) ->
-      tokens = @highlighter.tokensForLine(row)
+      tokens = @highlighter.tokensForRow(row)
       $$.pre class: 'line', ->
         if tokens.length
           for token in tokens
diff --git a/src/atom/highlighter.coffee b/src/atom/highlighter.coffee
index 8aa977732..fe30518af 100644
--- a/src/atom/highlighter.coffee
+++ b/src/atom/highlighter.coffee
@@ -2,24 +2,29 @@ module.exports =
 class Highlighter
   buffer: null
   tokenizer: null
-  lineTokens: []
+  tokensByRow: []
 
   constructor: (@buffer) ->
     @buildTokenizer()
-    @tokenizeLines()
+    @tokensByRow = @tokenizeRows('start', 0, @buffer.lastRow())
+
+    @buffer.on 'change', (e) =>
+      { preRange, postRange } = e
+      postRangeTokens = @tokenizeRows('start', postRange.start.row, postRange.end.row)
+      @tokensByRow[preRange.start.row..preRange.end.row] = postRangeTokens
 
   buildTokenizer: ->
     Mode = require("ace/mode/#{@buffer.modeName()}").Mode
     @tokenizer = (new Mode).getTokenizer()
 
-  tokenizeLines: ->
-    @lineTokens = []
+  tokenizeRows: (state, start, end) ->
+    for row in [start..end]
+      { state, tokens } = @tokenizeRow(state, row)
+      tokens
 
-    state = "start"
-    for line in @buffer.getLines()
-      { state, tokens } = @tokenizer.getLineTokens(line, state)
-      @lineTokens.push tokens
+  tokenizeRow: (state, row) ->
+    @tokenizer.getLineTokens(@buffer.getLine(row), state)
 
-  tokensForLine: (row) ->
-    @lineTokens[row]
+  tokensForRow: (row) ->
+    @tokensByRow[row]