Exposure to and absorption of Guthion 50 W.P. (azinphos‐methyl) were estimated in orchardists from the Okanagan Valley in British Columbia who were involved in mixing, loading, and application with ultra‐low volume air blast equipment. Air monitoring and patch techniques were used to estimate exposure, and alkyl phosphate excretion and cholinesterase inhibition were measured to estimate absorption. All workers were issued with standardized cotton shirts, trousers, and long‐sleeved coveralls. All wore half‐face respirators, gloves, boots, and hats. Eight wore rubberized protective clothing in addition. The indirect method of measuring urinary metabolites appeared to be the most sensitive. All workers had quantifiable levels of alkyl phosphates following exposure, and the 24‐h urine samples provided a more reliable estimate than first morning voids. A high correlation was observed between 48‐h alkyl phosphate excretion and amount of active ingredient sprayed. A fluorescent tracer was added to the tank along with the Guthion. The finding of Guthion on patches beneath the clothing was confirmed by the presence of the tracer on the skin. With the ultralow‐volume application used in this study, the rubberized clothing did not appear to be significantly more protective than the heavy coverall. There was no significant depression of either red blood cell or serum cholinesterase activity in any workers.