diff --git a/ghc-bench.cabal b/ghc-bench.cabal
--- a/ghc-bench.cabal
+++ b/ghc-bench.cabal
@@ -5,7 +5,7 @@
 -- see: https://github.com/sol/hpack
 
 name:           ghc-bench
-version:        0.3.2
+version:        0.3.3
 synopsis:       Benchmark a Haskell development system
 description:    See the README at <https://github.com/sol/ghc-bench#readme>
 category:       Development
diff --git a/src/Benchmark/Type.hs b/src/Benchmark/Type.hs
--- a/src/Benchmark/Type.hs
+++ b/src/Benchmark/Type.hs
@@ -4,6 +4,7 @@
 , Benchmark
 , dependencies
 , dryRun
+, prepare
 , run
 
 , withLabel
@@ -55,6 +56,9 @@
   Utf8.putStrLn output
   return times
 
+prepare :: Benchmark () -> IO [(Label, Seconds)]
+prepare = execForest . dropMeasuredCommands . toForest
+
 run :: Benchmark () -> IO [(Label, Seconds)]
 run = execForest . toForest
 
@@ -151,6 +155,14 @@
 showArg arg
   | any isSpace arg = show arg
   | otherwise = pack arg
+
+dropMeasuredCommands :: [Command] -> [Command]
+dropMeasuredCommands = map \ case
+  SetEnv name value commands -> SetEnv name value (dropMeasuredCommands commands)
+  ChangeDirectory dir commands -> ChangeDirectory dir (dropMeasuredCommands commands)
+  Download blob -> Download blob
+  Call command args -> Call command args
+  Measure label _ -> Measure label []
 
 execForest :: [Command] -> IO [(Label, Seconds)]
 execForest = go mempty
diff --git a/src/Run.hs b/src/Run.hs
--- a/src/Run.hs
+++ b/src/Run.hs
@@ -2,6 +2,7 @@
   main
 
 , DryRun(..)
+, Prepare(..)
 , PrintQR(..)
 , parseOptions
 , run
@@ -53,15 +54,21 @@
 data DryRun = NoDryRun | DryRun
   deriving (Eq, Show, Bounded)
 
+data Prepare = NoPrepare | Prepare
+  deriving (Eq, Show, Bounded)
+
 data PrintQR = NoPrintQR | PrintQR
   deriving (Eq, Show, Bounded)
 
-parseOptions :: [FilePath] -> (DryRun, (PrintQR, [FilePath]))
-parseOptions = fmap parsePrintQR . parseDryRun
+parseOptions :: [FilePath] -> (DryRun, (Prepare, (PrintQR, [FilePath])))
+parseOptions = (fmap . fmap) parsePrintQR . fmap parsePrepare . parseDryRun
 
 parseDryRun :: [FilePath] -> (DryRun, [FilePath])
 parseDryRun = parseOption "dry-run"
 
+parsePrepare :: [FilePath] -> (Prepare, [FilePath])
+parsePrepare = parseOption "prepare"
+
 parsePrintQR :: [FilePath] -> (PrintQR, [FilePath])
 parsePrintQR = parseOption "qr"
 
@@ -71,7 +78,7 @@
   _ -> maxBound
 
 main :: [String] -> IO ()
-main (parseOptions -> (dryRun, (printQR, args))) = do
+main (parseOptions -> (dryRun, (prepare, (printQR, args)))) = do
 
   cacheDir <- getXdgDirectory XdgCache "ghc-bench"
   createDirectoryIfMissing True cacheDir
@@ -94,7 +101,7 @@
 
   putStr . unlines $ "" : SystemInfo.pretty system
 
-  times <- run cacheDir (withTempDirectory baseDir "build") dryRun args stage0 concurrency
+  times <- run cacheDir (withTempDirectory baseDir "build") dryRun prepare args stage0 concurrency
   unless (null times) do
     putStrLn "\ntimes:"
     for_ times \ (Label name, time) -> do
@@ -105,8 +112,8 @@
 
 type WithTempDirectory = forall a. (FilePath -> IO a) -> IO a
 
-run :: FilePath -> WithTempDirectory -> DryRun -> [String] -> FilePath -> Concurrency -> IO [(Label, Seconds)]
-run cacheDir withTemp dryRun args stage0 concurrency = requireDependencies >> case args of
+run :: FilePath -> WithTempDirectory -> DryRun -> Prepare -> [String] -> FilePath -> Concurrency -> IO [(Label, Seconds)]
+run cacheDir withTemp dryRun prepare args stage0 concurrency = requireDependencies >> case args of
   [] -> runAll
   [name] | Just action <- lookup name actions -> action
   _ -> die usage
@@ -131,12 +138,13 @@
     runAll = concat <$> sequence (map snd actions)
 
     actions :: [(String, IO [(Label, Seconds)])]
-    actions = map (fmap $ withTemp . runBenchmark dryRun) benchmarkActions
+    actions = map (fmap $ withTemp . runBenchmark dryRun prepare) benchmarkActions
 
     usage :: FilePath
-    usage = "\nusage: ghc-bench [ " <> List.intercalate " | " (map fst actions) <> " ] [ --dry-run ]"
+    usage = "\nusage: ghc-bench [ " <> List.intercalate " | " (map fst actions) <> " ] [ --dry-run ] [ --prepare ]"
 
-runBenchmark :: DryRun -> Benchmark () -> FilePath -> IO [(Label, Seconds)]
-runBenchmark dryRun action dir = case dryRun of
-  NoDryRun -> Benchmark.run $ Benchmark.cd dir action
-  DryRun -> Benchmark.dryRun $ Benchmark.cd dir action
+runBenchmark :: DryRun -> Prepare -> Benchmark () -> FilePath -> IO [(Label, Seconds)]
+runBenchmark dryRun prepare action dir = case (dryRun, prepare) of
+  (DryRun, _) -> Benchmark.dryRun $ Benchmark.cd dir action
+  (_, Prepare) -> Benchmark.prepare $ Benchmark.cd dir action
+  _ -> Benchmark.run $ Benchmark.cd dir action
diff --git a/test/RunSpec.hs b/test/RunSpec.hs
--- a/test/RunSpec.hs
+++ b/test/RunSpec.hs
@@ -5,18 +5,24 @@
 import README (ensureFile)
 
 import Run qualified
-import Run (DryRun(..), PrintQR(..))
+import Run (DryRun(..), Prepare(..), PrintQR(..))
 
 spec :: Spec
 spec = do
   describe "--dry-run" do
     it "prints commands" do
-      let run = Run.run "~/.cache/ghc-bench" ($ "<sandbox>") DryRun [] "/path/to/ghc-9.12.4" 20
+      let run = Run.run "~/.cache/ghc-bench" ($ "<sandbox>") DryRun NoPrepare [] "/path/to/ghc-9.12.4" 20
       capture_ run >>= ensureFile "test/dry-run" . encodeUtf8 . pack
 
   describe "parseOptions" do
     it "accepts --dry-run" do
-      Run.parseOptions ["--dry-run", "foo", "bar"] `shouldBe` (DryRun, (NoPrintQR, ["foo", "bar"]))
+      Run.parseOptions ["--dry-run", "foo", "bar"]
+        `shouldBe` (DryRun, (NoPrepare, (NoPrintQR, ["foo", "bar"])))
 
+    it "accepts --prepare" do
+      Run.parseOptions ["--prepare", "foo", "bar"]
+        `shouldBe` (NoDryRun, (Prepare, (NoPrintQR, ["foo", "bar"])))
+
     it "accepts --qr" do
-      Run.parseOptions ["--qr", "foo", "bar"] `shouldBe` (NoDryRun, (PrintQR, ["foo", "bar"]))
+      Run.parseOptions ["--qr", "foo", "bar"]
+        `shouldBe` (NoDryRun, (NoPrepare, (PrintQR, ["foo", "bar"])))