A high-performance liquid chromatographic (HPLC) assay has been developed for the identification and quantification of 12 barbiturates at toxic and therapeutic levels in plasma, urine, gastric content, postmortem blood, and tissues. The sample preparation procedure involves a single-step extraction for plasma, urine, and gastric contents, and a supplementary back-extraction for postmortem blood and tissues. Appropriate internal standards are used for quantification. A mu Bondapak C18 column is used with a mobile phase of 40% methanol and (NH4)2HPO4 (0.05M). The barbiturates are detected at 240 and 290 nm. This method is rapid, sensitive, reproducible, relatively selective, and applicable to a great variety of biological fluids; it has been used regularly in forensic and clinical toxicological analyses.