diff --git a/R/modal.R b/R/modal.R
index 9b15188cf..939edeb28 100644
--- a/R/modal.R
+++ b/R/modal.R
@@ -1,4 +1,7 @@
-#' Show a modal dialog
+#' Show or remove a modal dialog
+#'
+#' This causes a modal dialog to be displayed in the client browser, and is
+#' typically used with \code{\link{modalDialog}}.
 #'
 #' @param ui UI content to show in the modal.
 #' @param session The \code{session} object passed to function given to
@@ -15,8 +18,6 @@ showModal <- function(ui, session = getDefaultReactiveDomain()) {
       deps = res$deps
     )
   )
-
-  invisible()
 }
 
 #' @rdname showModal
@@ -28,14 +29,124 @@ removeModal <- function(session = getDefaultReactiveDomain()) {
 
 #' Create a modal dialog UI
 #'
+#' This creates the UI for a modal dialog, using Bootstrap's modal class. Modals
+#' are typically used for showing important messages, or for presenting UI that
+#' requires input from the user, such as a username and password input.
+#'
 #' @param ... UI elements for the body of the modal dialog box.
 #' @param title An optional title for the dialog.
-#' @param footer UI for footer. Use \coode{NULL} for no footer.
+#' @param footer UI for footer. Use \code{NULL} for no footer.
 #' @param dismissable If \code{TRUE}, the modal dialog can be dismissed by
 #'   clicking outside the dialog box, or be pressing the Escape key. If
 #'   \code{FALSE} (the default), the modal dialog can't be dismissed in those
 #'   ways; instead it must be dismissed by clicking on the dismiss button, or
 #'   from a call to \code{\link{removeModal}} on the server.
+#'
+#' @examples
+#' if (interactive()) {
+#' # Display an important message that can be dismissed only by clicking the
+#' # dismiss button.
+#' shinyApp(
+#'   ui = basicPage(
+#'     actionButton("show", "Show modal dialog")
+#'   ),
+#'   server = function(input, output) {
+#'     observeEvent(input$show, {
+#'       showModal(modalDialog(
+#'         title = "Important message",
+#'         "This is an important message!"
+#'       ))
+#'     })
+#'   }
+#' )
+#'
+#'
+#' # Display a message that can be dismissed by clicking outside the modal dialog,
+#' # or by pressing Esc.
+#' shinyApp(
+#'   ui = basicPage(
+#'     actionButton("show", "Show modal dialog")
+#'   ),
+#'   server = function(input, output) {
+#'     observeEvent(input$show, {
+#'       showModal(modalDialog(
+#'         title = "Somewhat important message",
+#'         "This is a somewhat important message.",
+#'         dismissable = TRUE,
+#'         footer = NULL
+#'       ))
+#'     })
+#'   }
+#' )
+#'
+#'
+#' # Display a modal that requires valid username and password input.
+#' shinyApp(
+#'   ui = basicPage(
+#'     actionButton("show", "Show modal dialog"),
+#'     verbatimTextOutput("loginInfo")
+#'   ),
+#'   server = function(input, output) {
+#'     # A string with the current login status. This is in a reactiveValues
+#'     # object so that it can trigger reactivity.
+#'     vals <- reactiveValues(loginStatus = "Not logged in.")
+#'
+#'     # Attempt logging in with a username and password, returning TRUE if
+#'     # successful and FALSE if not.
+#'     login <- function(username, password) {
+#'       # In a real-world use case, this would check against some sort of user
+#'       # database instead of just checking that the values are identical to
+#'       # hard-coded values.
+#'       if (identical(username, "user1") && identical(password, "pass1")) {
+#'         vals$loginStatus <- paste0('Logged in as "', username, '"')
+#'         return(TRUE)
+#'
+#'       } else {
+#'         vals$loginStatus <- "Not logged in."
+#'         return(FALSE)
+#'       }
+#'     }
+#'
+#'     # Return the UI for a modal dialog with username/password inputs.
+#'     # If 'failed' is TRUE, then display a message that the previous username
+#'     # and password were invalid.
+#'     loginModal <- function(failed = FALSE) {
+#'       modalDialog(
+#'         textInput("username", "Username"),
+#'         passwordInput("password", "Password"),
+#'         span('(Try logging in with "user1" and "pass1")'),
+#'         if (failed)
+#'           div(tags$b("Invalid username/password", style = "color: red;")),
+#'
+#'         footer = tagList(
+#'           modalButton("Cancel"),
+#'           actionButton("login", "Log in")
+#'         )
+#'       )
+#'     }
+#'
+#'     observeEvent(input$show, {
+#'       showModal(loginModal())
+#'     })
+#'
+#'     # When login button is pressed, attempt to log in. If successful, remove the
+#'     # modal. If not show another modal, but this time with a failure message.
+#'     observeEvent(input$login, {
+#'       if (login(input$username, input$password)) {
+#'         removeModal()
+#'       } else {
+#'         showModal(loginModal(failed = TRUE))
+#'       }
+#'     })
+#'
+#'     # Display current login status
+#'     output$loginInfo <- renderText({
+#'       vals$loginStatus
+#'     })
+#'   }
+#' )
+#'
+#' }
 #' @export
 modalDialog <- function(..., title = NULL, footer = modalButton("Dismiss"),
                         dismissable = FALSE) {
@@ -53,7 +164,7 @@ modalDialog <- function(..., title = NULL, footer = modalButton("Dismiss"),
         if (!is.null(footer)) div(class = "modal-footer", footer)
       )
     ),
-    tags$script("$('#shiny-modal').modal().focus(); ")
+    tags$script("$('#shiny-modal').modal().focus();")
   )
 }
 
diff --git a/man/modalDialog.Rd b/man/modalDialog.Rd
index 4f5f1be3f..d33f1b8f8 100644
--- a/man/modalDialog.Rd
+++ b/man/modalDialog.Rd
@@ -12,7 +12,7 @@ modalDialog(..., title = NULL, footer = modalButton("Dismiss"),
 
 \item{title}{An optional title for the dialog.}
 
-\item{footer}{UI for footer. Use \coode{NULL} for no footer.}
+\item{footer}{UI for footer. Use \code{NULL} for no footer.}
 
 \item{dismissable}{If \code{TRUE}, the modal dialog can be dismissed by
 clicking outside the dialog box, or be pressing the Escape key. If
@@ -21,6 +21,114 @@ ways; instead it must be dismissed by clicking on the dismiss button, or
 from a call to \code{\link{removeModal}} on the server.}
 }
 \description{
-Create a modal dialog UI
+This creates the UI for a modal dialog, using Bootstrap's modal class. Modals
+are typically used for showing important messages, or for presenting UI that
+requires input from the user, such as a username and password input.
+}
+\examples{
+if (interactive()) {
+# Display an important message that can be dismissed only by clicking the
+# dismiss button.
+shinyApp(
+  ui = basicPage(
+    actionButton("show", "Show modal dialog")
+  ),
+  server = function(input, output) {
+    observeEvent(input$show, {
+      showModal(modalDialog(
+        title = "Important message",
+        "This is an important message!"
+      ))
+    })
+  }
+)
+
+
+# Display a message that can be dismissed by clicking outside the modal dialog,
+# or by pressing Esc.
+shinyApp(
+  ui = basicPage(
+    actionButton("show", "Show modal dialog")
+  ),
+  server = function(input, output) {
+    observeEvent(input$show, {
+      showModal(modalDialog(
+        title = "Somewhat important message",
+        "This is a somewhat important message.",
+        dismissable = TRUE,
+        footer = NULL
+      ))
+    })
+  }
+)
+
+
+# Display a modal that requires valid username and password input.
+shinyApp(
+  ui = basicPage(
+    actionButton("show", "Show modal dialog"),
+    verbatimTextOutput("loginInfo")
+  ),
+  server = function(input, output) {
+    # A string with the current login status. This is in a reactiveValues
+    # object so that it can trigger reactivity.
+    vals <- reactiveValues(loginStatus = "Not logged in.")
+
+    # Attempt logging in with a username and password, returning TRUE if
+    # successful and FALSE if not.
+    login <- function(username, password) {
+      # In a real-world use case, this would check against some sort of user
+      # database instead of just checking that the values are identical to
+      # hard-coded values.
+      if (identical(username, "user1") && identical(password, "pass1")) {
+        vals$loginStatus <- paste0('Logged in as "', username, '"')
+        return(TRUE)
+
+      } else {
+        vals$loginStatus <- "Not logged in."
+        return(FALSE)
+      }
+    }
+
+    # Return the UI for a modal dialog with username/password inputs.
+    # If 'failed' is TRUE, then display a message that the previous username
+    # and password were invalid.
+    loginModal <- function(failed = FALSE) {
+      modalDialog(
+        textInput("username", "Username"),
+        passwordInput("password", "Password"),
+        span('(Try logging in with "user1" and "pass1")'),
+        if (failed)
+          div(tags$b("Invalid username/password", style = "color: red;")),
+
+        footer = tagList(
+          modalButton("Cancel"),
+          actionButton("login", "Log in")
+        )
+      )
+    }
+
+    observeEvent(input$show, {
+      showModal(loginModal())
+    })
+
+    # When login button is pressed, attempt to log in. If successful, remove the
+    # modal. If not show another modal, but this time with a failure message.
+    observeEvent(input$login, {
+      if (login(input$username, input$password)) {
+        removeModal()
+      } else {
+        showModal(loginModal(failed = TRUE))
+      }
+    })
+
+    # Display current login status
+    output$loginInfo <- renderText({
+      vals$loginStatus
+    })
+  }
+)
+
+}
 }
 
diff --git a/man/showModal.Rd b/man/showModal.Rd
index 021c15b16..0332036ba 100644
--- a/man/showModal.Rd
+++ b/man/showModal.Rd
@@ -3,7 +3,7 @@
 \name{showModal}
 \alias{removeModal}
 \alias{showModal}
-\title{Show a modal dialog}
+\title{Show or remove a modal dialog}
 \usage{
 showModal(ui, session = getDefaultReactiveDomain())
 
@@ -16,7 +16,8 @@ removeModal(session = getDefaultReactiveDomain())
 \code{shinyServer}.}
 }
 \description{
-Show a modal dialog
+This causes a modal dialog to be displayed in the client browser, and is
+typically used with \code{\link{modalDialog}}.
 }
 \seealso{
 \code{\link{modalDialog}} for examples.
diff --git a/srcjs/modal.js b/srcjs/modal.js
index ea684451f..532192819 100644
--- a/srcjs/modal.js
+++ b/srcjs/modal.js
@@ -1,19 +1,29 @@
 exports.modal = {
 
+  // Show a modal dialog. This is meant to handle two types of cases: one is
+  // that the content is a Bootstrap modal dialog, and the other is that the
+  // content is non-Bootstrap. Bootstrap modals require some special handling,
+  // which is coded in here.
   show: function({ html='', deps=[] } = {}) {
-    // Get existing DOM element for this ID, or create if needed.
+
+    // If there was an existing Bootstrap modal, then there will be a modal-
+    // backdrop div that was added outside of the modal wrapper, and it must be 
+    // removed; otherwise there can be multiple of these divs.
+    $('.modal-backdrop').remove();
+
+    // Get existing wrapper DOM element, or create if needed.
     let $modal = $('#shiny-modal-wrapper');
     if ($modal.length === 0) {
       $modal = $('<div id="shiny-modal-wrapper"></div>');
       $('body').append($modal);
-    }
 
-    // When the inner modal is hidden, remove the entire thing, including
-    // wrapper. This is meant to work with Bootstrap modal dialogs.
-    $modal.on('hidden.bs.modal', function() {
-      exports.unbindAll($modal);
-      $modal.remove();
-    });
+      // If the wrapper's content is a Bootstrap modal, then when the inner
+      // modal is hidden, remove the entire thing, including wrapper.
+      $modal.on('hidden.bs.modal', function() {
+        exports.unbindAll($modal);
+        $modal.remove();
+      });
+    }
 
     // Set/replace contents of wrapper with html.
     exports.renderContent($modal, { html: html, deps: deps });
@@ -22,14 +32,11 @@ exports.modal = {
   remove: function() {
     const $modal = $('#shiny-modal-wrapper');
 
-    // Look for a Bootstrap modal dialog inside the modal wrapper
-    const $bsmodal = $modal.find(".modal");
-
-    if ($bsmodal.length > 0) {
-      // If the modal wrapper contains a Bootstrap modal dialog, trigger hide
-      // event. This will trigger the hidden.bs.modal callback taht we set in
-      // show(), which unbinds and removes the element.
-      $bsmodal.modal('hide');
+    // Look for a Bootstrap modal and if present, trigger hide event. This will
+    // trigger the hidden.bs.modal callback that we set in show(), which unbinds
+    // and removes the element.
+    if ($modal.find('.modal').length > 0) {
+      $modal.find('.modal').modal('hide');
 
     } else {
       // If not a Bootstrap modal dialog, simply unbind and remove it.