Pyricularia grisea fungus which causing rice blast disease is one of the main pathological races threats to rice crop in Egypt and worldwide.  Thirty isolates out of known 144 strains of this fungus were selected according to geographical locations. Isolates of P. grisea,  were analyzed by SSR markers to determine the amount of genetic variability among these races. Sixteen primers out of 26 were amplified  and produced a total of 83 alleles . Number of alleles per marker ranged from 3 for C7-1.4, P9-0.4 and P9-1.9 to 9 for H6-0.8-5 primer, with an average of 5.2. The polymorphic information content (PIC) values were high for all markers with an average of 0.70 and ranged from as low as 0.51 for C7-1. 4 to high of 0.83 for H6-0.8–5 marker. UPGMA-cluster-analysis based on genetic distance coefficients clearly separated all isolates of  P. grisea.  The results showed that the studied isolates were classified into 4 lineages by cutting off the dendrogram at 0.70 similar linkage level. Group D was the major group and represented most of those isolates. The average similarities within cluster was greater than the average similarities between clusters. In general, the  results of this investigation confirmed that microsatellite markers would be useful and suitable for determining the genetic diversity in P. grisea populations.