A rapid and simple gas chromatographic method for the simultaneous determination of malathion, parathion, fenitrothion, diazinon and carbaryl in drinking water is presented. A fused-silica SE-54 column was used for the separation of the insecticides and was split into two specific detectors; electron-capture and nitrogen-phosphorus detectors by using column switching. A water sample was extracted with methylene chloride. The organic phase was evaporated and the residue was derivatized with pentafluoropropionic acid anhydride. The detection limit was below 0.1 ng/ml and the calibration curves showed good linearity with r = 0.998 approximately 1.000. The method was sensitive, reproducible and simple enough to permit the reliable routine analysis of the pesticides in drinking water.