Exposure to parathion of orchard spraymen operating concentrate (8X to 12X) air-blast spray machines has been compared with that of spraymen using conventional dilute (1X) air-blast spray machines. The calculated potential dermal exposure for operators of concentrate spray equipment was 27.9 mg/hr as compared to 19.4 mg/hr with the high-volume equipment. The greater dermal exposure with the concentrate machine is primarily due to greater contamination of the hands. Potential respiratory exposure with the concentrate machine was 0.055 mg/hr of exposure, or about 2.7 times that determined for operators of conventional dilute machines (0.020 mg/hr). This greater respiratory exposure for operators of concentrate machines may be due to the greater probability of inhaling the smaller spray droplets produced by that type of machine. The results of the present study, as well as the good safety record of concentrate sprays, indicate that these techniques can be used safely provided that recommended precautions are followed.