On my Windows installation if I open a new multichannel audio file Audition's Audio Channel Mapping only shows Default Stereo Input. There appears to be no multichannel input mapping although the drop down menu allows me to select any two of the four available inputs from my Microbooks ASIO driver. 

So how do you get Audition to map more than two inputs at once for a surround recording?
ryclark wrote So how do you get Audition to map more than two inputs at once for a surround recording? |
Okay, I give in - I can't get this to work by any means.
But I can record 5.1 though with ASIO in multitrack view - no problem. Start with the 5.1 session, and allocate ASIO channels appropriately:

The session mixer will look like this:

And when you open the mixdown in Waveform view, those channels you can't record in are all filled up!

So it definitely works with ASIO. You can't set up a single input as such, but if you record into the 5.1 surround template, you get a 5.1 file as a result.