The determination of urinary alkylphosphates monitors occupational exposure to organophosphorus pesticides and insecticides. This paper describes a method for the quantitative determination of the following metabolites: O,O-dimethylphosphate (DMP), O,O-diethylphosphate (DEP), O,O-diethyldithiophosphate (DETP), O,O-dimethyldithiophosphate (DMDTP), O,O-diethyldithiophosphate (DEDTP), and O,O-dimethylthiophosphate (DMTP). The compounds are derivatized with pentafluorobenzylbromide into pentafluorobenzyl esters which are determined by gas chromatography with a capillary column of intermediate polarity and a flame photometric detector specific for phosphorus. Before the analytical gas chromatographic stage, the urinary extracts are purified on isolute SPE CN columns. The proposed method has a limit of detection of 2-3 micrograms/L at 62.5 micrograms/L and a mean recovery of the purification stage of 85.8-101.0% for all six compounds. The coefficient of variation of the analytical procedure was 7.9-11.9% for the six compounds. The low detection limits make this method suitable also for determining the six metabolites in the general population.