A case involving a fatal poisoning (suicide) by the insecticide malathion is described. The intact insecticide was found in the post-mortem blood and gastric contents at concentrations of 1.8 and 978 micrograms/ml, respectively. None of the insecticide was found in the autopsied liver tissue. Gas chromatography-mass spectrometry (GC-MS) techniques were used for the identification and quantification of malathion in the body fluids.