Blast disease caused by Magnaporthe grisea (Hebert) Barr. anamorph Pyricularia oryzae, is an important fungal disease of rice known to occur in most rice producing areas of the world. In Nepal, the disease causes 10%-20% yield reduction in susceptible varieties, but in severe case, it goes up to 80% to measure virulence of 5 isolates of P. grisea, obtained from various location, against 10 genotypes of rice, a shade house experiment was carried out under inoculated condition at NARC (Nepal Agricultural Research Council), Khumaltar, during August, 2015. Isolates from Gokarna and Madhyapur Thimi had highest aggressiveness, and it was lowest in Kirtipur and Lalitpur isolates. Considerable pathogenic variations were observed in the five isolates, however no distinct differential reactions were found on the genotypes. Highest disease severity was found in Taichung-176 and least in Manjushree, IR 87760-15-2-2-4, IR 70210-39-CPA-7-1 and NR 11105-B-B-20-2-1 under shade house.