<p>I've got a Excel VSTO 2005 application I need to debug, I've tried attaching to the process EXCEL.EXE in Visual Studio 2005 to no avail.</p>

<p>Does anyone know what to do in order to debug managed code running in a VSTO Excel Application?</p>

I haven't worked with Excel, but with VSTO in Word, attaching the debugger to the WINWORD process works, but makes it impossible to debug startup code, as it has already ran before you can attach.  In this case you can insert
```
```
Debugger.Launch();
```
```
which will stop your code and ask to attach a debugger.  It's about the best solution I could find.