The most common single substance encountered in toxicologic analysis is alcohol. The word alcohol indicated the compound ethanol. Alcohol almost invariably enters the body by ingestion of an alcoholic beverage. Concentration of alcohol in fermented beverages is expressed as percent by volume, while proof is used to express concentrations of alcohol in distilled beverages. Alcohol requires no preliminary digestion and, unlike most foods and drugs, is readily absorbed from the stomach. Approximately half of the absorption occurs by this route, with the remainder occurring by way of the small intestine. Absorbed alcohol is carried from the gastrointestinal tract to the liver, where it is eliminated through oxidation. Primary factors involved in the interpretation of postmortem results are the method of collection of samples for evaluation of the presence of alcohol, the choice of samples, and the preservation of the samples. In most jurisdictions a blood sample is chosen for analysis. Exceptions to the blood sample rule include embalmed bodies, persons sustaining severe internal injury affecting gastric contents, and persons surviving many hours after the fatal injury. There are three methods of determining the alcohol concentration in body fluids and tissues. The first is distillation of the alcohol and subsequent reaction with potassium dichromate and sulfuric acid. The second procedure involves using the enzyme alcohol dehydrogenase. In more recent years the third method, which employs gas chromatography, has been employed. Death due to acute alcoholic intoxication occurs at blood alcohol concentrations of 0.40 percent. In individuals with chronic debilitating diseases it can occur at lower concentrations. Tables and nine references are included. For related documents, see NCJ 69731-43 and 69745-47.