A gas chromatographic procedure for determining diazinon (333415) and parathion (56382) and their dialkyl metabolites in liver and kidney tissues was developed. Liver and kidney samples were homogenized in a mixture of hydrochloric-acid/ethanol/ethyl-acetate. After centrifugation, the supernatant was evaporated to dryness under nitrogen. The residue was redissolved in hexane and filtered. The filtrate was cleaned up by gel permeation chromatography utilizing elution with hexane and ethyl-acetate. The eluate was concentrated to 1 milliliter (ml), and a 0.1ml aliquot was taken for gas chromatographic determination of diazinon and parathion. The remaining 0.9ml was reserved for determining O,O-dimethylphosphate (813785) (DMP), O,O-diethylphosphate (598027) (DEP), O,O- dimethylphosphorothioate (28523797) (DMTP), O,O- dimethylphosphorodithioate (16001686) (DMDTP), O,O- diethylphosphorothioate (5871170) (DETP), and O,O- diethylphosphorodithioate (3454668) (DEDTP). The gas chromatograph had a flame photometric detector and utilized a DB-1701 column in the determination of diazinon and parathion. In the determination of DMP, DEP, DMTP, DMDTP, DETP, and DEDTP, the sample was transferred to an autosampler vial and derivatized with tetrabutylammonium-hydroxide. The sample was then analyzed by gas chromatography utilizing a DB-1 column. The detection limit for diazinon and parathion was 0.02 part per million (ppm). The detection limit for DMP, DEP, DMTP, DMDTP, DETP, and DEDTP was liver and kidney homogenates from pigeons that had been given diazinon or parathion.