Insecticide resistance in the small brown planthopper, Laodelphax striatellus (SBPH) was first recognized by Kimura12 for malathion and hexachlorocyclohexane in the middle 1960's. Ozaki and Kassai3 also reported the insecticide resistance for some other organophosphates and carbamates. Reduction of winter cereals culture and development of effective insecticides in the 1970s seemed to have suppressed occurrence of rice stripe disease which is transmitted by SBPH, and this rice insect became less important. Serious outbreak of the rice stripe disease, however, occurred in Kyushu district in 1985. 4'5 Furthermore, Sone et al. s reported disulfoton and propoxur resistance in SBPH colonies collected from various areas in 1991 and 1992. Thus insecticide resistance of SBPH has become a serious problem again. We collected SBPH from several districts to compare insecticide susceptibility and study mechanisms of resistance.