A spectrophotometric method for the determination of 1-naphthol in drinking water samples is described. The method is based on the coupling of 1-naphthol obtained from hydrolyzing of carbaryl with diazotized sulphanilic acid in an alkaline medium. Beer's law is obeyed in the range of 0.01-0.1 ppm of 1-naphthol. The proposed method is sensitive and rapid. Average 1-naphthol content of the drinking water samples was 9.05. The samples were obtained from their sources during one day after about 24 hours than rain.