diff --git a/src/milkwood_clj/core.clj b/src/milkwood_clj/core.clj
index 0138fbd..9b538f6 100644
--- a/src/milkwood_clj/core.clj
+++ b/src/milkwood_clj/core.clj
@@ -24,14 +24,15 @@ See http://codekata.pragprog.com/2007/01/kata_fourteen_t.html"
                         "The length of the sequences to analyse it into (integer)"
                         :parse-fn #(Integer. %)
                         :default 2])
-        file (arguments :file)]
+        file (arguments :file)
+        output (arguments :output)]
     (cond
      (= file nil) (print banner)
      (arguments :help) (print banner)
      true (synthesise/write-output
            (synthesise/compose-nonsense
             (analyse/analyse-file file (arguments :tuple-length))
-            (arguments :output-length))))
+            (arguments :output-length)) output))
     (flush)))
 
 
diff --git a/src/milkwood_clj/synthesise.clj b/src/milkwood_clj/synthesise.clj
index 9aa8ea8..68886db 100644
--- a/src/milkwood_clj/synthesise.clj
+++ b/src/milkwood_clj/synthesise.clj
@@ -159,7 +159,14 @@
    TODO: does not yet work. Should take an optional second argument,
       the file to write to if any (default to standard out).
 
-   output: a sequence of tokens to write."
-  [output]
-  (dorun (map write-token (top-and-tail output)))
-  (print "\n\n"))
+   output: a sequence of tokens to write;
+   destination: if not null, the name of the file to which to write it."
+  ([output destination]
+    (cond
+     destination
+     (let [text (with-out-str (write-output output))]
+       (spit destination text))
+     true (write-output output)))
+  ([output]
+    (dorun (map write-token (top-and-tail output)))
+    (print "\n\n")))
diff --git a/test/milkwood_clj/synthesise_test.clj b/test/milkwood_clj/synthesise_test.clj
index 71b161a..4d0891e 100644
--- a/test/milkwood_clj/synthesise_test.clj
+++ b/test/milkwood_clj/synthesise_test.clj
@@ -7,3 +7,9 @@
     (is (= (top-and-tail '("a" "b" "c" "?" "d" "e" "f" "." "g" "h" "i" "!")) '("d" "e" "f" "." "g" "h" "i" "!")))
     (is (= (top-and-tail '("a" "b" "c" "?" "d" "e" "f" "." "g" "h" "i")) '("d" "e" "f" ".")))
     ))
+
+(deftest write-output-test
+  (testing "Test output to file"
+    (is (= (do ;; (spit "test.out" "")
+             (write-output '("Test" "output" ".") "test.out")
+             (slurp "test.out"))) "Test output.")))