diff --git a/osu.Desktop/Beatmaps/IO/LegacyFilesystemReader.cs b/osu.Desktop/Beatmaps/IO/LegacyFilesystemReader.cs
index 711607b9df..31c7b4c365 100644
--- a/osu.Desktop/Beatmaps/IO/LegacyFilesystemReader.cs
+++ b/osu.Desktop/Beatmaps/IO/LegacyFilesystemReader.cs
@@ -19,15 +19,16 @@ namespace osu.Desktop.Beatmaps.IO
         }
     
         private string BasePath { get; set; }
+        private string[] Beatmaps { get; set; }
         private Beatmap FirstMap { get; set; }
     
         public LegacyFilesystemReader(string path)
         {
             BasePath = path;
-            var maps = ReadBeatmaps();
-            if (maps.Length == 0)
+            Beatmaps = Directory.GetFiles(BasePath, "*.osu").Select(f => Path.GetFileName(f)).ToArray();
+            if (Beatmaps.Length == 0)
                 throw new FileNotFoundException("This directory contains no beatmaps");
-            using (var stream = new StreamReader(ReadFile(maps[0])))
+            using (var stream = new StreamReader(ReadFile(Beatmaps[0])))
             {
                 var decoder = BeatmapDecoder.GetDecoder(stream);
                 FirstMap = decoder.Decode(stream);
@@ -36,7 +37,7 @@ namespace osu.Desktop.Beatmaps.IO
 
         public override string[] ReadBeatmaps()
         {
-            return Directory.GetFiles(BasePath, "*.osu").Select(f => Path.GetFileName(f)).ToArray();
+            return Beatmaps;
         }
 
         public override Stream ReadFile(string name)
diff --git a/osu.Game/Beatmaps/IO/OszArchiveReader.cs b/osu.Game/Beatmaps/IO/OszArchiveReader.cs
index 13a4db5db5..036ce07128 100644
--- a/osu.Game/Beatmaps/IO/OszArchiveReader.cs
+++ b/osu.Game/Beatmaps/IO/OszArchiveReader.cs
@@ -1,5 +1,8 @@
 using System;
 using System.IO;
+using System.Linq;
+using Ionic.Zip;
+using osu.Game.Beatmaps.Formats;
 
 namespace osu.Game.Beatmaps.IO
 {
@@ -11,32 +14,48 @@ namespace osu.Game.Beatmaps.IO
             {
                 using (var stream = storage.GetStream(path))
                 {
-                    // TODO: detect if osz
-                    return false;
+                    if (!ZipFile.IsZipFile(stream, false))
+                        return false;
+                    using (ZipFile zip = ZipFile.Read(stream))
+                        return zip.Entries.Any(e => e.FileName.EndsWith(".osu"));
                 }
             });
         }
     
-        private Stream Archive { get; set; }
+        private ZipFile Archive { get; set; }
+        private string[] Beatmaps { get; set; }
+        private Beatmap FirstMap { get; set; }
     
         public OszArchiveReader(Stream archive)
         {
-            Archive = archive;
+            Archive = ZipFile.Read(archive);
+            Beatmaps = Archive.Entries.Where(e => e.FileName.EndsWith(".osu"))
+                .Select(e => e.FileName).ToArray();
+            if (Beatmaps.Length == 0)
+                throw new FileNotFoundException("This directory contains no beatmaps");
+            using (var stream = new StreamReader(ReadFile(Beatmaps[0])))
+            {
+                var decoder = BeatmapDecoder.GetDecoder(stream);
+                FirstMap = decoder.Decode(stream);
+            }
         }
 
         public override string[] ReadBeatmaps()
         {
-            throw new NotImplementedException();
+            return Beatmaps;
         }
 
         public override Stream ReadFile(string name)
         {
-            throw new NotImplementedException();
+            ZipEntry entry = Archive.Entries.SingleOrDefault(e => e.FileName == name);
+            if (entry == null)
+                throw new FileNotFoundException();
+            return entry.OpenReader();
         }
 
         public override Metadata ReadMetadata()
         {
-            throw new NotImplementedException();
+            return FirstMap.Metadata;
         }
     }
 }
\ No newline at end of file
diff --git a/osu.Game/osu.Game.csproj b/osu.Game/osu.Game.csproj
index ed8d91d6e7..e50e0847d8 100644
--- a/osu.Game/osu.Game.csproj
+++ b/osu.Game/osu.Game.csproj
@@ -55,6 +55,9 @@
     <Reference Include="SQLite-net">
       <HintPath>..\packages\sqlite-net-pcl.1.2.0\lib\portable-net45+wp8+wpa81+win8+MonoAndroid10+MonoTouch10+Xamarin.iOS10\SQLite-net.dll</HintPath>
     </Reference>
+    <Reference Include="DotNetZip">
+      <HintPath>..\packages\DotNetZip.1.10.1\lib\net20\DotNetZip.dll</HintPath>
+    </Reference>
   </ItemGroup>
   <ItemGroup>
     <Compile Include="Beatmaps\Beatmap.cs" />
diff --git a/osu.Game/packages.config b/osu.Game/packages.config
index d40da68750..1f14b0038d 100644
--- a/osu.Game/packages.config
+++ b/osu.Game/packages.config
@@ -4,6 +4,7 @@ Copyright (c) 2007-2016 ppy Pty Ltd <contact@ppy.sh>.
 Licensed under the MIT Licence - https://raw.githubusercontent.com/ppy/osu/master/LICENCE
 -->
 <packages>
+  <package id="DotNetZip" version="1.10.1" targetFramework="net45" />
   <package id="Newtonsoft.Json" version="9.0.1" targetFramework="net45" />
   <package id="ppy.OpenTK" version="1.1.2225.3" targetFramework="net45" />
   <package id="sqlite-net-pcl" version="1.2.0" targetFramework="net45" />