The potential hazard to workers exposed to the organophosphorus pesticide, parathion, in formulating plants was studied. Potential dermal and respiratory exposure near certain work stations was determined. Calculations were based on the use of minimum protection (no respirator, shirt with short sleeves and open collar, no hat, no gloves, and with the assumption that the clothing worn gave complete protection of body areas covered). This was to arrive at values that might reflect the maximum potential exposure that could occur in different work situations where proper protective gear was not utilized. Mean dermal exposure for all workers was 67.3 mg/hr and the mean respiratory value was 0.62 mg/hr of work activity. Workers at the bagging machine were subjected to greater exposure than mixers or workers who stacked filled bags on pallets, operated the bag closing machine, or packed filled bags in cardboard cartons for storage or shipment.