One hundred forty Pyricularia grisea isolates were collected from the six main rice growing governorates; Kafrelsheikh, Beheira, Sharkia, Gharbia, Dakahlia and Damietta, and from different research stations during 2008, 2009 and 2010 growing seasons. The isolates were identified to their group races as IA (1); IB (12); IC (15); ID (45); IE (1); IF (4); IG (22); IH (32) and II (8) using the international differential varieties under greenhouse conditions. Vegetative compatibility groups (VCGs) among the races were studied through producing nitrate nonutilizing (nit) mutants for the races on chlorate minimal medium (CMM). The results revealed that the nit mutants were grouped into eight VCGs. VCG 1 included members of the IB race group (70.59 %). VCG 2 included members of IC race group with 87.5% and two isolates were identified as IH and II. The largest group, VCG 3 included 44 isolates, most of these isolates were identified as ID (86.36 %). All isolates in VCG 4 were identified as IF. 95.65% of isolates in VCG 5 represented IG and one belonged to II (4.35%). All isolates in VCG 6 corresponded to IH (96.43 %), and only one as ID. VCG 7 included eight isolates, 5 isolates represented ID and one each of IG, IF and IH. Only one isolate was identified as IE race group in VCG 8. The reaction among different nit mutants was examined using a scanning electron microscope and revealed that heterokaryon, incompatibility and inhibition zone were observed. This investigation revealed that the correspondence between VCGs and races ranged from 62.5 to 100 %; however, the latter percentage was relevant to very small number of isolates