A fatality in which diazinon was the suspected toxic agent was investigated. Samples of omental tissue, blood, and liver tissue were examined by gas chromatography and thin layer chromatography. Diazinon was found in the omentum (at a level of 5.1 mg/kg) and blood (in a trace amount), but no diazinon was found in the liver tissue. Methods are given for the extraction of diazinon from omental fat, the purification of these extracts by sweep co-distillation and fat precipitation, and for an estimation of the amount of diazinon present. It is not possible to determine whether the low level found arose from chronic occupational exposure, accidental dermal contact, or ingestion of a lethal dose.