A spectrophotometric method for the determination of carbaryl in soil and strawberry fruit samples is described. The method is based on the coupling of l-naphthol obtained from hydrolysing carbaryl with diazotised sulphanilic acid in an alkaline medium to form p-(4-hydroxyl-1-naphtylaza)benzenesulphonic acid which has a maximum absorbance at 475 nm. Beer's law is obeyed in the range of 0.01-0.1 ppm of carbaryl. The proposed method is sensitive and rapid. The average carbaryl content of strawberry fruits was 6.03 ppm and the average l-naphthol content of soil samples was 16.29. The samples were obtained from their sources during 1 day after approx. 24 h of rain. (C) 1998 Elsevier Science B.V. All rights reserved.