diff --git a/zephyr/static/js/composebox_typeahead.js b/zephyr/static/js/composebox_typeahead.js
index 7735973666..b63e3a4382 100644
--- a/zephyr/static/js/composebox_typeahead.js
+++ b/zephyr/static/js/composebox_typeahead.js
@@ -20,13 +20,33 @@ function render_pm_object(person) {
     return person.full_name + " <" + person.email + ">";
 }
 
-exports.update_typeahead = function() {
-    private_message_mapped = {};
-    private_message_typeahead_list = [];
-    $.each(people_list, function (i, obj) {
-        var label = render_pm_object(obj);
-        private_message_mapped[label] = obj;
-        private_message_typeahead_list.push(label);
+function add_to_known_recipients(recipient_data, count_towards_autocomplete_preference) {
+    var name_string = render_pm_object(recipient_data);
+    if (private_message_mapped[name_string] === undefined) {
+        private_message_mapped[name_string] = recipient_data;
+        private_message_mapped[name_string].count = 0;
+        private_message_typeahead_list.push(name_string);
+    }
+    if (count_towards_autocomplete_preference) {
+        private_message_mapped[name_string].count += 1;
+    }
+}
+
+exports.known_to_typeahead = function (recipient_data) {
+    return private_message_mapped[render_pm_object(recipient_data)] !== undefined;
+};
+
+exports.update_all_recipients = function (recipients) {
+    $.each(recipients, function (idx, recipient_data) {
+        add_to_known_recipients(recipient_data, false);
+    });
+};
+
+exports.update_your_recipients = function (recipients) {
+    $.each(recipients, function (idx, recipient_data) {
+        if (recipient_data.email !== email) {
+            add_to_known_recipients(recipient_data, true);
+        }
     });
 };
 
@@ -147,9 +167,7 @@ exports.initialize = function () {
     });
 
     $( "#private_message_recipient" ).typeahead({
-        source: function (query, process) {
-            return private_message_typeahead_list;
-        },
+        source: private_message_typeahead_list,
         items: 4,
         highlighter: composebox_typeahead_highlighter,
         matcher: function (item) {
@@ -159,18 +177,33 @@ exports.initialize = function () {
             if (! current_recipient.match(/\S/)) {
                 return false;
             }
-            // Case-insensitive (from Bootstrap's default matcher).
+
+            // Case-insensitive.
             return (item.toLowerCase().indexOf(current_recipient.toLowerCase()) !== -1);
         },
+        sorter: function (matches) {
+            matches.sort(function (x, y) {
+                var x_count = private_message_mapped[x].count;
+                var y_count = private_message_mapped[y].count;
+
+                if (x_count > y_count) {
+                    return -1;
+                } else if (x_count < y_count) {
+                    return 1;
+                }
+                return 0;
+            });
+
+            return matches;
+        },
         updater: function (item) {
-            var obj = private_message_mapped[item];
             var previous_recipients = get_cleaned_pm_recipients(this.query);
             previous_recipients.pop();
             previous_recipients = previous_recipients.join(", ");
             if (previous_recipients.length !== 0) {
                 previous_recipients += ", ";
             }
-            return previous_recipients + obj.email + ", ";
+            return previous_recipients + private_message_mapped[item].email + ", ";
         },
         stopAdvance: true // Do not advance to the next field on a tab or enter
     });
diff --git a/zephyr/static/js/typeahead_helper.js b/zephyr/static/js/typeahead_helper.js
index 78a1fe9d40..2279a0eaeb 100644
--- a/zephyr/static/js/typeahead_helper.js
+++ b/zephyr/static/js/typeahead_helper.js
@@ -13,13 +13,6 @@ exports.autocomplete_needs_update = function (needs_update) {
 
 exports.update_autocomplete = function () {
     stream_list.sort();
-    people_list.sort(function (x, y) {
-        if (x.email === y.email) return 0;
-        if (x.email < y.email) return -1;
-        return 1;
-    });
-
-    composebox_typeahead.update_typeahead();
     search.update_typeahead();
     autocomplete_needs_update = false;
 };
diff --git a/zephyr/static/js/zephyr.js b/zephyr/static/js/zephyr.js
index 4f80a44ab5..b473011eff 100644
--- a/zephyr/static/js/zephyr.js
+++ b/zephyr/static/js/zephyr.js
@@ -1,7 +1,6 @@
 var message_array = [];
 var message_dict = {};
 var subject_dict = {};
-var people_set = {};
 
 var viewport = $(window);
 
@@ -16,9 +15,7 @@ var get_updates_params = {
 };
 
 $(function () {
-    $.each(people_list, function (idx, person) {
-        people_set[person.email] = true;
-    });
+    composebox_typeahead.update_all_recipients(people_list);
 });
 
 // The "message groups", i.e. blocks of messages collapsed by recipient.
@@ -422,23 +419,31 @@ function add_message_metadata(dummy, message) {
         message.display_reply_to = get_huddle_recipient(message, 'full_name');
 
         involved_people = message.display_recipient;
+
+        if (message.sender_email === email) {
+            composebox_typeahead.update_your_recipients(involved_people);
+        } else {
+            composebox_typeahead.update_all_recipients(involved_people);
+        }
         break;
 
     case 'personal':
         message.is_personal = true;
 
-        if (message.sender_email === email) { // that is, we sent the original message
-            message.reply_to = message.display_recipient.email;
-            message.display_reply_to = message.display_recipient.full_name;
-        } else {
-            message.reply_to = message.sender_email;
-            message.display_reply_to = message.sender_full_name;
-        }
-
         involved_people = [message.display_recipient,
                            {'email': message.sender_email,
                             'full_name': message.sender_full_name}];
 
+        if (message.sender_email === email) { // that is, we sent the original message
+            message.reply_to = message.display_recipient.email;
+            message.display_reply_to = message.display_recipient.full_name;
+            composebox_typeahead.update_your_recipients(involved_people);
+        } else {
+            message.reply_to = message.sender_email;
+            message.display_reply_to = message.sender_full_name;
+            composebox_typeahead.update_all_recipients(involved_people);
+        }
+
         break;
     }
 
@@ -446,8 +451,7 @@ function add_message_metadata(dummy, message) {
     $.each(involved_people, function (idx, person) {
         // Do the hasOwnProperty() call via the prototype to avoid problems
         // with keys like "hasOwnProperty"
-        if (! Object.prototype.hasOwnProperty.call(people_set, person.email)) {
-            people_set[person.email] = true;
+        if (! composebox_typeahead.known_to_typeahead(person)) {
             people_list.push(person);
             typeahead_helper.autocomplete_needs_update(true);
         }