Farmers may be exposed to fungicides through both personal application and use of treated seed. Most epidemiology studies rely on personal application to assess exposure. We explored the extent of potential exposure via use of treated seed using data from a large cohort of licensed pesticide applicators from Iowa and North Carolina. Potential secondary fungicide exposure due to treated seed was calculated by crop by multiplying the average percent of seed treated by those reporting raising that crop but not applying fungicide. This potential exposure was present for every crop with treated seed (corn, soybean, wheat, cotton, potato, and peanut), and was highest for corn (71%) and soybean farmers (19%). Potential secondary fungicide exposure was more common in Iowa than in North Carolina since most Iowa farmers plant corn and soybeans and few report applying fungicides. Owing to its widespread use on corn, potential secondary captan exposure may occur among the 90% of the individuals planting corn. The relative intensity of secondary fungicide exposure associated with planting treated seed is anticipated to be lower than actively applying fungicide. Limited data suggest that exposure during planting may be approximately 4% of actively applying fungicide; while seed transfer operations may have similar levels of exposure to personal application (80-200%). Measurement data are necessary to characterize the patterns of exposure related to the use of fungicide-treated seed and to determine whether this route of exposure is an important contributor to fungicide exposure among farmers.