diff --git a/README.md b/README.md
--- a/README.md
+++ b/README.md
@@ -51,6 +51,11 @@
     help
       Print this help text.
     
+    pretty
+      Pretty-print expressions using Unicode logic symbols. Only employ this
+      option if your console is Unicode-aware. If pretty-printing is already
+      enabled, using this command will disable it.
+    
     exit
       Quit the program.
     
@@ -113,6 +118,9 @@
     F T F | F
     F F T | T
     F F F | F
+
+You can enable pretty-printing while in interactive mode by using the `pretty`
+command.
 
 
 Using Hatt in other programs
diff --git a/hatt.cabal b/hatt.cabal
--- a/hatt.cabal
+++ b/hatt.cabal
@@ -1,5 +1,5 @@
 Name:               hatt
-Version:            0.3
+Version:            1.0
 Stability:          experimental
 
 Synopsis:           A truth table generator for classical propositional logic.
diff --git a/src/hatt.hs b/src/hatt.hs
--- a/src/hatt.hs
+++ b/src/hatt.hs
@@ -10,32 +10,33 @@
 import System.Console.CmdArgs
 import System.IO
 
-data HattOpts = HattOpts
-    { evaluate    :: String
-    , interactive :: Bool
-    , pretty      :: Bool
-    } deriving (Show, Data, Typeable)
-
 data Command = Exit
              | Help
+             | Pretty
              | Eval Expr
              | Error String
 
-hattOpts :: HattOpts
-hattOpts = HattOpts
+data ProgramMode = ProgramMode
+  { evaluate    :: String
+  , interactive :: Bool
+  , pretty      :: Bool
+  } deriving (Show, Data, Typeable)
+
+programMode :: ProgramMode
+programMode = ProgramMode
   { evaluate    = "" &= typ  "EXPRESSION"
                      &= help "Print the truth table for the given expression"
   , interactive = False &= help "Enter interactive mode"
   , pretty      = False &= help "Use Unicode logic symbols"
-  } &= summary "Hatt 0.3, (c) Benedict Eastaugh 2011"
+  } &= summary "Hatt 1.0, (c) Benedict Eastaugh 2011"
     &= program "hatt"
 
 main :: IO ()
-main = do opts <- cmdArgs hattOpts
+main = do opts <- cmdArgs programMode
           let expStr    = evaluate opts
               interMode = interactive opts
               evalMode  = (not . null) expStr
-              printer   = if pretty opts then show else showAscii
+              printer   = selectPrinter opts
           
           -- If the --evaluate flag is passed with an expression, print the
           -- truth table for that expression.
@@ -48,17 +49,26 @@
           -- program; otherwise, enter interactive mode.
           if evalMode && not interMode
             then return ()
-            else putStrLn replIntroText >> repl printer
+            else putStrLn replIntroText >> repl opts
 
-repl :: (Expr -> String) -> IO ()
-repl p = do putStr "> "
-            hFlush stdout
-            cmd <- getLine
-            case parseCommand cmd of
-              Exit        -> return ()
-              Help        -> putStr   replHelpText         >> repl p
-              (Eval expr) -> putStr   (truthTableP p expr) >> repl p
-              (Error err) -> putStrLn ("Error: " ++ err)   >> repl p
+repl :: ProgramMode -> IO ()
+repl mode = do putStr "> "
+               hFlush stdout
+               cmd <- getLine
+               case parseCommand cmd of
+                 Exit        -> return ()
+                 Help        -> putStr replHelpText
+                                >> repl mode
+                 Pretty      -> putStrLn ppMessage
+                                >> repl (mode {pretty = not isPretty})
+                 (Eval expr) -> putStr (truthTableP printer expr)
+                                >> repl mode
+                 (Error err) -> putStrLn ("Error: " ++ err)
+                                >> repl mode
+  where
+    printer   = selectPrinter mode
+    isPretty  = pretty mode
+    ppMessage = (if isPretty then "Dis" else "En") ++ "abling pretty-printing."
 
 eval :: (Expr -> String) -> String -> String
 eval p str = case parseExpr "" str of
@@ -67,10 +77,11 @@
 
 parseCommand :: String -> Command
 parseCommand input = case cmd . words . dropWhile isSpace $ input of
-                       ""     -> Error "you must enter an expression or a command."
-                       "exit" -> Exit
-                       "help" -> Help
-                       _      -> eval_ input
+                       ""       -> Error "you must enter an expression or a command."
+                       "exit"   -> Exit
+                       "help"   -> Help
+                       "pretty" -> Pretty
+                       _        -> eval_ input
   where
     cmd []    = ""
     cmd ws    = map toLower . head $ ws
@@ -86,11 +97,16 @@
 
 replHelpText :: String
 replHelpText = unlines
-  [ "Hatt's interactive mode has a couple of commands."
+  [ "Hatt's interactive mode has several commands."
   , ""
   , "help"
   , "  Print this help text."
   , ""
+  , "pretty"
+  , "  Pretty-print expressions using Unicode logic symbols. Only employ this"
+  , "  option if your console is Unicode-aware. If pretty-printing is already"
+  , "  enabled, using this command will disable it."
+  , ""
   , "exit"
   , "  Quit the program."
   , ""
@@ -115,3 +131,6 @@
   , ""
   , "If none of this makes any sense, try reading the README file."
   ]
+
+selectPrinter :: ProgramMode -> (Expr -> String)
+selectPrinter m = if pretty m then show else showAscii