Booting Mountain Lion in 32-Bit Mode

There are certain applications I use that required me to boot in 32-bit mode in OS X 10.7 (Lion). I could do this by holding down the "2" and "3" keys upon startup. This no longer works since I have upgraded to OS X 10.8.

Is there still a way I can force Mountain Lion to boot in 32-bit mode?

As you have a definitive no - here is a workaround that most people are pursuing in this case. Run Lion in a virtualized environment on top of Mountain Lion. The commercial products like VMware Fusion, Parallels and VirtualBox all might assist you until those applications can be updated or replaced.

Of course, you could dual boot most hardware but a virtual solution might work longer term if you choose to upgrade hardware.

No,

Mountain Lion only boots using a 64-bit kernel which does not support loading 32-bit kernel extensions.

via Arstechnica