IDL's SYSTIME DOES capture CPU seconds. It makes a query via the C interface to the operating system via C's "systime()" function. Different operating systems have different "granularity" for the value they return back to this query. Windows is notorious for providing poor precision in this case. For Windows users, one of our engineers posted in RSI's User Contrib Library site a small DLM interface for much more precise time-querying in IDL. Though it is written in C, it can automatically be called from within IDL. Check out his contribution at the following URL: http://www.rsinc.com/code...k/search.asp?FID=262 James Jones