diff --git a/sc2reader/engine/plugins/__init__.py b/sc2reader/engine/plugins/__init__.py
index d506b69b..40cd12c8 100644
--- a/sc2reader/engine/plugins/__init__.py
+++ b/sc2reader/engine/plugins/__init__.py
@@ -5,3 +5,4 @@
 from sc2reader.engine.plugins.selection import SelectionTracker
 from sc2reader.engine.plugins.context import ContextLoader
 from sc2reader.engine.plugins.gameheart import GameHeartNormalizer
+from sc2reader.engine.plugins.composition import CompositionTracker
diff --git a/sc2reader/engine/plugins/composition.py b/sc2reader/engine/plugins/composition.py
new file mode 100644
index 00000000..0b484dbe
--- /dev/null
+++ b/sc2reader/engine/plugins/composition.py
@@ -0,0 +1,98 @@
+from collections import Counter
+from sc2reader.engine.events import PluginExit
+
+
+class CompositionTracker(object):
+    """
+    Generates a list of Counter (a fancy dict) for each player that stores
+    unit composition at regular intervals. This is stored as player.composition
+    """
+    name = 'CompositionTracker'
+
+    # these pop up independently of units actually constructed
+    EXCLUDED_NAMES = set([
+        'ReaperPlaceholder',
+        'Interceptor'
+        'Locust',
+        'LocustMP',
+        'Broodling',
+        'BroodlingEscort',  # the guys that fly with the Brood Lord
+    ])
+
+    def __init__(self, interval=15, remove_on_death=True, normalize_names=True):
+        """
+        interval defines how often we to extract compositions in seconds
+        remove_on_death determines if they still count after dying
+        normalize_names tries to fix up some awkward type names
+        """
+        self.frame_interval = interval << 4
+        self.remove_on_death = remove_on_death
+        self.normalize_names = normalize_names
+
+    def handleEndGame(self, event, replay):
+        for player in replay.players:
+            unit_ranges = self.get_unit_ranges(player, replay.frames)
+
+            player.compositions = [Counter() for i in
+                    range(replay.frames // self.frame_interval + 1)]
+            num_compositions = len(player.compositions)
+
+            for name, start, end in unit_ranges:
+                # if you are born on the frame exactly, you count. else, round up
+                # if you die on the frame, you don't count. else, starting cutting it off
+                start_index = (start - 1) // self.frame_interval + 1
+                end_index = ((end - 1) // self.frame_interval + 1) if self.remove_on_death \
+                        else num_compositions
+                for index in range(start_index, end_index):
+                    player.compositions[index][name] += 1
+
+    def print_compositions(self, replay):
+        """
+        for debugging
+        """
+        for player in replay.players:
+            for i, composition in enumerate(player.compositions):
+                print(i * self.frame_interval / 16)
+                print(composition)
+                for unit, count in composition.items():
+                    print('    {}\t\t{}'.format(unit, count))
+
+    def get_unit_ranges(self, player, frames):
+        """
+        type history is usually just a single entry with the birthday, but sometimes it changes
+        break history up into ranges with distinct types and store those
+        the stuff about cur_ is trying to coalesce types when they just change the suffix
+        """
+        unit_ranges = []
+        for unit in player.units:
+            if unit.name.startswith('Beacon') or unit.name in self.EXCLUDED_NAMES or \
+                    unit.hallucinated:
+                continue
+
+            intervals = unit.type_history.items()
+            cur_name = self.normalize_type(intervals[0][1])
+            cur_start = intervals[0][0]
+            for interval in intervals[1:]:
+                new_name = self.normalize_type(interval[1])
+                if new_name != cur_name:
+                    unit_ranges.append((cur_name, cur_start, interval[0]))
+                    cur_name = new_name
+                    cur_start = interval[0]
+
+            unit_ranges.append((cur_name, cur_start, unit.died_at or frames))
+        return unit_ranges
+
+    def normalize_type(self, cur_type):
+        """
+        remove spurious type changes
+        """
+        name = cur_type.name
+
+        if not self.normalize_names:
+            return name
+
+        for suffix in ('Flying', 'Lowered', 'Burrowed', 'Assault', 'Sieged', 'Uprooted'):
+            if name.endswith(suffix):
+                name = name[:-len(suffix)]
+        return name
+
diff --git a/test_replays/composition/composition.SC2Replay b/test_replays/composition/composition.SC2Replay
new file mode 100644
index 00000000..b20b02e3
Binary files /dev/null and b/test_replays/composition/composition.SC2Replay differ
diff --git a/test_replays/test_all.py b/test_replays/test_all.py
index ba7c0ea8..a3b93fd6 100644
--- a/test_replays/test_all.py
+++ b/test_replays/test_all.py
@@ -360,6 +360,15 @@ def test_gameheartnormalizer_plugin(self):
         self.assertEqual(replay.teams[1].players[0].name, 'LiquidTaeJa')
         self.assertEqual(replay.winner, replay.teams[0])
 
+    def test_composition_tracker_plugin(self):
+        from sc2reader.engine.plugins import CompositionTracker
+        sc2reader.engine.register_plugin(CompositionTracker())
+
+        replay = sc2reader.load_replay('test_replays/composition/composition.SC2Replay')
+
+        self.assertTrue(replay.players[0].compositions)
+        self.assertEqual(replay.players[0].compositions[20]['Reaper'], 1)
+
     def test_replay_event_order(self):
         replay = sc2reader.load_replay("test_replays/event_order.SC2Replay")