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Notes: Abstract Loader/mixers/applicators and workers engaged in thinning and harvesting grapes in the central valley of California, were monitored for exposure to captan. Urinalyses for the captan metabolite, tetrahydrophthalimide (THPI), was intended to be the biological, index for exposure to captan. Dislodgeable residues of captan and THPI on foliage and grapes were measured as well as levels found in high volume air samplers placed in the field at the time of foliage sampling. Loader/mixer/ applicators were monitored following an application of a 10% dust and a wettable powder (W.P.) formulation just prior to thinning operations, and again at harvest with a W.P. formulation. Loader/ mixer/applicators were also monitored with and without respiratory protection with each treatment. The half-life of captan for the dust application was 12.8 days, and 19.6 days for W.P. Tetrahydrophthalimide levels were very low in all the field and clothing samples and were not a significant factor in worker exposure. Levels of captan in the air during the loading/mixing operation were higher. Although there were exceptions, gloves contained the highest levels of residues in the loader/mixer/applicators and the field workers. The relative levels found on the patches were reflective of the work habits of the workers. The applicators of the 10% dust had the highest captan levels in the personnel air samplers and on their mask or respirator pads. The results from the urine analysis, although THPI was found, showed no significant differences in trends between the pre- and post-exposure samples except possibly the individual who wore the respirator during the dusting operation. Pre- and post-exposure urine samples of field workers engaged in the thinning and harvesting operation showed no significant differences except workers engaged in the dusted plot. Dislodgeable foliage levels and glove residues from workers are used to measure potential dermal exposure, and since these two parameters were lowest in the dusted plots coupled with the same or slightly higher levels found in the high volume air samples in the dusted plot, they support the importance of investigating inhalation as a primary source of exposure to captan. Estimated dermal exposure in mg/person in relation to each pound of captan applied by loader/mixer/applicators was highest with those engaged in the dusting operation; the applicators during the harvest operation had much lower levels compared to the loader/ mixer/applicators during the thinning operation.