The behavioral effects induced by methyl-n-amyl ketone (110430) (MAK) exposure were studied. Rats received from one to eight intraperitoneal injections (group I) of 18, 37, 74, or 175 milligrams per kilogram (mg/kg) MAK, or were exposed to MAK aerosols (Group II) of 800 to 1,900 parts per million (ppm) daily for 6 or 8 hours. Following inhalation exposures, the rats were given injections of 37, 74, or 175mg/kg MAK. All rats in both experimental groups were tested daily after exposure for 1 hour on a multiple fixed ratio, fixed interval reinforcement schedule. Testing continued for 8 months, and pre- and postexposure response rates were compared. No consistent changes in response rate were observed in group I rats exposed to 18mg/kg. At 37mg/kg and above, there was a significant dose related decrease in the response rate. Group II rats exposed to aerosol concentrations below 1,500ppm had no behavioral changes; those exposed to concentrations above 1,500ppm had decreased response rates. Postexposure MAK injections also decreased response rates. Over the course of the study, the magnitude of the response reduction decreased, suggesting that MAK tolerance developed. The investigators did not observe a general performance deterioration over the course of the study, and they suggest that the effective MAK doses might have been much greater if the animals had received an extended course of exposure.