When green leafhopper (GLH: N.virescens Distant) was fed on resistant varieties of rice (O. sativa L.), its population decreased remarkably in the first 2 generations, but after that it increased steadily. Namely, GLH biotypes which are able to develop and reproduce on each resistant variety were established. Thus, 5 GLH biotypes were selected on 5 resistant varieties, Pankhari 203, ASD 7, Ptb 8, TAPL 796 and IR 42 respectively, and the relationship between GLH biotypes and rice varieties was analyzed. There was specific or vertical resistance of rice varieties to GLH biotypes: Each of Pankhari 203, Ptb 8 and IR 42 was resistant to all biotypes developed on other varieties but susceptible to the biotype developed on it. Most of resistant cultivars or lines from West Malaysia and IRRI were considered to have a same resistant gene as that of IR 42 derived from Ptb 18, because they were all susceptible to the GLH biotype developed on IR 42. On the basis of the results of this study, the authors recommend that Pankhari 203, Ptb 8 and TAPL 796 are the genetic source of GLH resistance to be used after the breakdown of IR 42 which has already been planted for several years in Malaysia.