By rearingNephotettix virescens(Distant) populations on resistant ‘Pankhari 203’ and ‘IR8’ for 10 generations, colonies virulent to the resistant cultivars, as indicated by plant damage ratings,N. virescenssurvival, and population growth, were selected. Testing the colonies on cultivars that have the same major gene for resistance as the cultivar upon which they were selected indicated increased virulence on some cultivars but not on others. Minor genes play an important role in determining the degree of cross virulence ofN. virescenson different cultivars.