interference check - 2 linked files

[cbaze]

In the interference check, I can select between the current model and one linked file only. Let's say I import a MEP and a Structural .rvt into my Arch file. I can't run an interference check between MEP and Structural?!

[Dimitri Harvalias]

Unfortunately it's strictly a one to one check when using the internal tools. So to ensure no interference you would need to run three checks (STR - ARCH, MEP - ARCH and MEP-STR)
If you need a more robust tools take a look at Navisworks. You'll find it much faster to perform checks as well as navigate. You can import/export from/to a variety of 3D file formats and you gain the ability to do hard and 'soft' interferences. Navis models are easily navigated because they are so light weight.