A total of 142 isolates of Pyricularia grisea were isolated from five Governorates and tested for pathotype diversity on rice seedlings of eight international differential varieties, included twelve Egyptian commercial cultivars and ten Japanese differential varieties (JDVs). Tested isolates were differentiated into thirty pathotypes. For the year 2008, IH race group represented the most frequent phenotype, being 42.22%, followed by IG and II, being 15.56% for both. However, in 2009, ID and IG were the common race groups, being 37.88 and 22.72% in respectively. In 2010, ID race group was still the common race group (64.52%), followed by IB (19.35%) and IC (12.9%). Egyptian commercial rice cultivars tested against P. grisea isolates displayed variable reactions. Cultivars Giza 178, Sakha 102, Sakha 103 and Hybrid 1 were resistant to all isolates. While, cvs. Giza 177, Reiho and Giza 181 rice cultivars were infected by 5, 10 and 17 out of the tested isolates, respectively. The susceptible rice cultivars Giza 176, Sakha 104, Giza 159, Sakha 101 and Giza 171 displayed different levels of susceptibility. Concerning the effectiveness of resistance genes, Pi-Z gene was the highest effective in blast control with 93.80%, followed by Pi-i plus Pi-Ks with 87.22%. In opposite, Pi-ta2 and Pi-a were the least effective genes with 55.77 and 22.78%, respectively. The variability in the pathogen and the resistance identified of some genotypes used in this study are further investigated to develop superior, adapted germplasm for use in rice breeding programs in Egypt.