Between May and early July in 1986, samples of treated (finished) water were collected after rainfall from 33 public water supplies using surface water sources. These samples were analyzed for 37 pesticide compounds. Fourteen water supplies also collected samples from their surface water source prior to treatment to determine the effectiveness of treatment with regard to pesticide removal. Detectable concentrations of one or more of ten pesticides were found in the treated water from 30 of the 33 water supplies tested. Individual pesticides and the number of supplies in which they were detected were: atrazine, 30; cyanazine (Bladex), 26; metolachlor (Dual), 21; alachlor (Lasso), 17; carbofuran (Furadan), 9; metribuzin (Sencor), 4; 2,4-D, 2; and, trifluralin (Treflan), butylate (Sutan) and dicamba (Banvel), 1 each. Study results indicate that current conventional water treatment technology is ineffective at substantial reduction of pesticide concentrations or elimination of pesticides from drinking water. Further, the study suggests that current pesticide monitoring requirements of the Safe Drinking Water Act are inadequate.