The mutagenicity of urine from spray applicators in 12 greenhouses in 1986 has been evaluated. The workers served as their own controls. Urine samples reflecting pesticide exposure were collected at the end of the day of application and a corresponding control sample was collected 3 d later. Using Salmonella typhimurium bacterial tester strains TA98 and TA100 with and without S9 activation, seven workers showed no significant differences (p less than 0.05) in the mutagenicity of their exposed and control urine. Of the five remaining workers, three, who wore no respirators, showed significantly higher (p less than 0.05) concentrations of mutagens in their exposed urine sample as compared to their respective controls. The mutagenicity of certain of the compounds applied by these latter workers is discussed.