Ten commercial rice cultivars were evaluated to partial resistance for blast disease under greenhouse conditions at Rice Research and Training Center, Sakha, in 2000 season. Ten isolates of Pyriculuria grisea collected from different locations were tested and identified on the international differential rice varieties (IDV) and commercial rice cultivars. Five from the new cultivars i.e Giza 177, Giza 178, Sakha 101, Sakha 102, and Sakha 104 showed susceptible reactions to one or two of the tested isolates. Giza 159 and Giza 171 were susceptible to all tested isolates. The isolates placed in seven race-groups i.e. two isolates for each of group IA, IC and ID, whereas, one isolate conformed each of IB, IG, IH and II races.Two races I A-69 (Isolate No.5) as highly virulent and IG-1 (isolate No.52) as a less virulent on the IDV were selected to study partial resistace parameters. Total number of lesions / leaf or plants, sporulation density and lesions type that developed differed greatly among cultivars. The number of lesions decreased by increasing leaf age. High numbers of necrotic spots (type 1-2) on new rice cultivars than on old cultivars could be attributed to hypersensitivity phenomenon. The new rice cultivars had lower number of type 4 lesions and less number of spores / lesion (sporulation capacity) than the old cultivars. This is may reflect a level of partial resistance in addition to major gene effects on the new cultivars than the old ones.