The brown planthopper, Nilaparvata lugens Stål (Hemiptera: Delphacidae), exhibits geographic and temporal variations in its virulence and damage characteristics on cultivated rice varieties, so the potential ecological risk of the nontarget effectiveness of Bt rice on different brown planthopper populations should be addressed. The nontarget effects of two Bt rice lines T2A-1 (Cry2A rice) and T1C-19 (Cry1C rice) on six brown planthopper populations with geographical, virulent, and resistant variations were evaluated. Populations differed significantly in relation to brown planthopper nymphal survival, nymphal duration, and female adult weight. T2A-1 and T1C-19 did not affect the ecological fitness parameters of brown planthopper compared with the parental non-Bt rice MH63. Both esterase and glutathione-S-transferase activities differed between brown planthopper populations. Esterase activity of some brown planthopper populations was significantly affected by the rice lines. It is important to take account of these findings in management ofnontarget brown planthopper in Cry2A or Cry1C rice in the future.