The potential hazard to workers exposed to the organophosphorus pesticide, disulfoton, in fertilizer-pesticide mixing plants was studied. Potential dermal and respiratory exposure, as well as levels of pesticide in air near certain work stations, was determined. Exposure was found to be much higher during dry mixing of granular pesticide with pelletized fertilizer than during the wet mixing process involving injection of liquid concentrate pesticide into the system to evenly impregnate the fertilizer. Calculations based on the highest exposure values obtained indicate that a worker may be subjected to as much as 4.3% of a toxic dose per hour of exposure during dry mix operations, but only 0.4% of a toxic dose per hour of exposure during wet mix operations. Levels of disulfoton in most of the air samples taken in the plant during dry mix operations exceeded the 0.1 mg/cu m threshold limit value for that compound; however, none of the samplings during wet mix operations exceeded that level.