Cocaine and cocaethylene concentrations in blood and tissues at early stages postmortem (0-6 hours) were investigated using alcohol-treated rats. Gas chromatography/mass spectrometry following a liquid/liquid extraction procedure was used to detect those drugs. In a group treated with cocaine and ethanol orally, the liver lost more than 25 percent of the cocaine present at death after 1 hour. Conversely, the hepatic cocaethylene concentrations at this time reached more than twice those at death. Thereafter, the hepatic concentrations of cocaine and cocaethylene were maintained at a constant level until 6 hours postmortem. Similar results were obtained with rats given cocaine intramuscularly. No changes were observed in the cocaine and cocaethylene concentrations in any other tissues during the 6 hour postmortem period. The forensic pathologist and toxicologist should be aware of these phenomena when selecting postmortem specimens for the analysis of cocaine and cocaethylene and take them into account when interpreting the results. Tables, figures, references