It seems that xmkmf is no longer available on Snow Leopard, which makes sense given that it's part of the deprecated imake package. Unfortunately, there's stuff out there that still needs it. I was trying to install x3270 on my Mac because I'm extremely intrigued by MVS/380 and I would need a 3270 emulator for it. For whatever reason, fink doesn't have a x3270 package, but MacPorts does. When trying to install it from MacPorts, though, it errored out with configure: error: 'Cannot find xmkmf' .