Thanks to all that responded. Yes...I need to look into pre-generating all of the random numbers that may be needed. It will not be trivial in the case of this particular application I am implementing, but is absolutely worth considering. Robert Kern's response was more along the lines of what I was trying to convey though. Does that particular bit of code require optimization? Thanks, -Mark -- Dr. Mark P. Miller Department of Biology 5305 Old Main Hill Utah State University Logan, UT 84322-5305 USA

<><><><><><><><><><><><><><><>< http://www.biology.usu.edu/people/facultyinfo.asp?username=mpmbio http://www.marksgeneticsoftware.net