diff --git a/depends.cabal b/depends.cabal
--- a/depends.cabal
+++ b/depends.cabal
@@ -1,5 +1,5 @@
 name:             depends
-version:          0.0.0
+version:          0.0.1
 license:          MIT
 license-file:     LICENSE
 copyright:        (c) 2013 Simon Hengel
@@ -23,6 +23,11 @@
       src
   main-is:
       Main.hs
+  other-modules:
+      GhcPkg
+      Cabal
+      Run
+      Config
   build-depends:
       base    == 4.*
     , process
diff --git a/src/Cabal.hs b/src/Cabal.hs
new file mode 100644
--- /dev/null
+++ b/src/Cabal.hs
@@ -0,0 +1,38 @@
+module Cabal where
+
+import Data.List
+import Data.Version
+
+import GhcPkg
+
+format :: String -> [Package] -> [Package] -> String
+format name mainDeps testDeps = unlines [
+    "-- NOTE:"
+  , "--"
+  , "-- This file was generated from dependencies.yaml.  To regenerate it run"
+  , "-- `depends`."
+  , "--"
+  , "name: " ++ name
+  , "version: 0.0.0"
+  , "build-type: Simple"
+  , "cabal-version: >= 1.8"
+  , ""
+  , "executable " ++ name
+  , "  ghc-options: -Wall"
+  , "  hs-source-dirs: src"
+  , "  main-is: Main.hs"
+  ] ++ builDepends mainDeps ++ unlines [
+    ""
+  , "test-suite test"
+  , "  type: exitcode-stdio-1.0"
+  , "  ghc-options: -Wall -Werror"
+  , "  hs-source-dirs: test, src"
+  , "  main-is: Main.hs"
+  ] ++ builDepends testDeps
+  where
+    builDepends deps
+      | null deps = ""
+      | otherwise = "  build-depends:\n      " ++ intercalate "\n    , " (map formatDep deps) ++ "\n"
+
+    formatDep :: Package -> String
+    formatDep (Package n v) = n ++ " == " ++ showVersion v
diff --git a/src/Config.hs b/src/Config.hs
new file mode 100644
--- /dev/null
+++ b/src/Config.hs
@@ -0,0 +1,20 @@
+{-# LANGUAGE OverloadedStrings #-}
+module Config where
+
+import           Control.Applicative
+import           Data.Maybe
+import           System.Directory
+import           System.FilePath
+import qualified Data.Yaml.Config as Yaml
+
+type Config = (String, [String], [String])
+
+load :: FilePath -> IO Config
+load path = do
+  yaml <- Yaml.load path
+  dir <- listToMaybe . reverse . splitDirectories <$> getCurrentDirectory
+  let name = fromMaybe "dependencies" $ Yaml.lookup "name" yaml <|> dir
+      deps sec = fromMaybe [] (Yaml.lookup sec yaml)
+      mainDeps = deps "main"
+      testDeps = deps "test"
+  return (name, mainDeps, testDeps)
diff --git a/src/GhcPkg.hs b/src/GhcPkg.hs
new file mode 100644
--- /dev/null
+++ b/src/GhcPkg.hs
@@ -0,0 +1,70 @@
+module GhcPkg where
+
+import           Control.Applicative
+import           Control.Monad
+import           Data.Char
+import           Data.Maybe
+import qualified Data.Version as Version
+import           Data.Version hiding (parseVersion)
+import           Text.ParserCombinators.ReadP
+import           System.Process
+import           System.Exit
+import           System.IO
+import           System.Environment
+
+data Package = Package {
+  packageName :: String
+, packageVersion :: Version
+} deriving (Eq, Show, Ord)
+
+dependencies :: Package -> IO [Package]
+dependencies p = do 
+  r <- uncurry readProcess c ""
+  let err = die ("Could not parse the output of `" ++ showCommand c ++ "`!")
+  maybe err return (parseDependencies r)
+  where
+    c = ("ghc-pkg", ["field", showPackage p, "depends"])
+    showCommand = unwords . uncurry (:)
+
+parseDependencies :: String -> Maybe [Package]
+parseDependencies xs = case xs of
+  'd':'e':'p':'e':'n':'d':'s':':':ys ->
+    mapM (stripPackageFingerprint >=> parsePackage) (dropBoring ys)
+  _ -> Nothing
+  where
+    dropBoring = filter (/= "builtin_rts") . map strip . lines
+
+stripPackageFingerprint :: String -> Maybe String
+stripPackageFingerprint xs = case (dropWhile (/= '-') . reverse) xs of
+  '-':ys -> (Just . reverse) ys
+  _ -> Nothing
+
+latest :: String -> IO Package
+latest name = do
+  p <- strip <$> readProcess "ghc-pkg" ["latest", name] ""
+  let err = die (show p ++ " is not a valid package name!")
+  maybe err return (parsePackage p)
+
+parsePackage :: String -> Maybe Package
+parsePackage xs = do
+  (name, version) <- splitVersion xs
+  Package name <$> parseVersion version
+  where
+    splitVersion ys = case (break (== '-') . reverse) ys of
+      (version, '-' : name) -> Just (reverse name, reverse version)
+      _ -> Nothing
+
+showPackage :: Package -> String
+showPackage (Package name version) = name ++ "-" ++ showVersion version
+
+parseVersion :: String -> Maybe Version
+parseVersion = fmap fst . listToMaybe . filter ((== "") . snd) . readP_to_S Version.parseVersion
+
+strip :: String -> String
+strip = dropWhile isSpace . reverse . dropWhile isSpace . reverse
+
+die :: String -> IO a
+die err = do
+  name <- getProgName
+  hPutStrLn stderr (name ++ ": " ++ err)
+  exitFailure
diff --git a/src/Run.hs b/src/Run.hs
new file mode 100644
--- /dev/null
+++ b/src/Run.hs
@@ -0,0 +1,41 @@
+module Run (run) where
+
+import           Control.Applicative
+import           Data.List
+import           Data.Char
+import           Data.Ord
+import           Data.Map (Map)
+import qualified Data.Map as Map
+import           Control.Monad.Trans.State
+import           Control.Monad.IO.Class
+
+import           Config
+import           GhcPkg
+import qualified Cabal
+
+type Cache = Map Package [Package]
+
+run :: IO ()
+run = do
+  (name, mainDeps, testDeps) <- load "dependencies.yaml"
+  mainPackages <- mapM latest mainDeps
+  testPackages <- mapM latest testDeps
+  m <- execStateT (mapM_ transitiveDependencies mainPackages) Map.empty
+  t <- execStateT (mapM_ transitiveDependencies testPackages) m
+  writeFile (name ++ ".cabal") (Cabal.format name (keys m) (keys t))
+  where
+    keys = sortByPackageName . Map.keys
+    sortByPackageName :: [Package] -> [Package]
+    sortByPackageName = sortBy (comparing (map toLower . packageName))
+
+transitiveDependencies :: Package -> StateT Cache IO [Package]
+transitiveDependencies p = do
+  c <- get
+  case Map.lookup p c of
+    Just xs -> return xs
+    Nothing -> do
+      xs <- liftIO (dependencies p)
+      ys <- concat <$> mapM transitiveDependencies xs
+      let r = p : xs ++ ys
+      modify (Map.insert p r)
+      return r