Concentrations of four popular pestisides; buprofezin, fenobucarb (BPMC), fthalide, and pyridaphenthion, in the air were measured at two locations in Nagano prefecture for three days after aerial application in August 1991. Fenobucarb was detected for three days, whereas the others were done only for one day. The maximum values of the concentrations of buprofezin, fenobucarb, fthalide, and pyridaphenthion were 2, 5, 10, and 0.2mg/m³, which are equivalent to 1/500, 1/830, 1/3000, 1/120 of each threshold concentration for safety proposed by the Japanese Society of Industrial Hygiene (1989, 1990), respectively.