Phytophthora root and stem rot of soybean is a destructive disease of soybean in Iran. During 1998–2005, 142 isolates from soil and diseased soybean plants were collected and tested. Race identification was made possible by inoculating Rps differential soybean cultivars and lines. Of the 142 isolates tested, 110 isolates belonged to race 1 and 32 isolates belonged to race 3. Race 1 was domi nant in soil and diseased plant samples. There was no variability in virulence of Phytophthora sojae between the areas surveyed.