The apparent organophosphate poisoning of a greenhouse pesticide applicator, caused by exposure to sulfotepp (3689245) fumigant, was examined in this study. A field investigation at the greenhouse, after the patient returned to work, and a telephone survey of greenhouse operators were conducted. One of four workers indicated that he failed to notice any odor or symptoms during application, yet only one applicator required medical attention. All personal protective equipment (PPE) appeared fit and was handled properly. The same four workers who had previously applied the fumigate demonstrated the preparation and application of the pesticide for investigators. After 45 minutes, when the application process was completed, the applicators left the scene and removed their PPE in a safe area. Once again, the same applicator became ill, although less seriously, and the same three applicators smelled the fumigant, although it was less noticeable. Of the 53 companies which participated in the telephone survey, 81% reported the use of fumigants, and 70% the use of fumigants containing sulfotepp. Of the 43 companies using fumigants, 77% claimed the use of respirators during application. Although three workers had become ill in the 43 companies surveyed, two despite the use of PPE, no worker had sought medical attention. Recommendations included that the labels of the fumigants examined in this study, Plantfume-103 and Fulex, indicate the use of supplied air during application and that pesticide prefilters, cartridges and canisters should bear warnings that they are not to be used with fumigants. Improved work practices could also reduce exposures.