Simon, I'm now ready to "make". I have set up a mk/build.mk with the just following line: prefix = /home/djs25/testghc I should then be able to invoke my test ghc as /home/djs25/testghc/ghc-5.02.2/bin/ghc I have some questions: 1. How does ghc know where to get its libraries from? Will it pick them up from /home/djs25/testghc/ghc-5.02.2/bin/ghc or /usr/lib/ghc-5.02.2 2. What do I put in build.mk to change the version? I would like /home/djs25/testghc/ghc-5.02.2/bin/ghc --version to give The Glorious Glasgow Haskell Compilation System, version 5.02.2test so that I know am picking up my test version rather than the real thing. Many thanks, Dominic.