Mutagenicity and benzo [a] pyrene content in extracts from smoke of mosquito coils and nonsmoke mosquito mats were investigated in the Salmonella/S9 mutagenicity test. Extracts from smoke of mosquito coils showed mutagenic response with or without S9mix to TA100, and with S9mix to TA98. Mutagenic activity (TA100, +S9mix) of extracts from mosquito coils smoke was approximately 1/3-7/10 times that of cigarette smoke. Volatile matters generated from nonsmoke mosquito mats were slightly mutagenic to TA100 in the presence of S9mix.