Existing PT programs do not address the complexity of postmortem forensic toxicology. These programs do not include decomposed samples and solid tissues; therefore, the FAA, in July 1991, started such a PT program. This program is used to professionally develop and maintain technical currency on a voluntary, inter-laboratory, and self-evaluation basis, as well as to quantifiably assess methods in the absence and presence of interfering substances. There are currently approximately 30 laboratories in the program. Functioning under various governmental/nongovernmental agencies and academic institutions, these laboratories represent a cross-section of the country. PT samples are distributed quarterly, and result summaries are sent to the participants, while maintaining their anonymity. Since the inception of the program, 28 PT samples encompassing whole blood, plasma, urine, kidney, or liver, with (or without) drugs, metabolites, and common chemicals (nicotine, caffeine, B-phenylethylamine, etc.) have been analyzed by the participants. Analytical findings were generally consistent with the anticipated values, but they were dependent on the nature and conditions of the specimens and types of the added analytes. Some incidences of false positives of concern were noted as well. This PT program is one of the few programs recommended by the American Board of Forensic Toxicology in which laboratories may participate for their accreditation by the Board. It is anticipated that this PT program will continue to play a critical part in supporting the quality assurance/quality control component of forensic toxicology, thereby enhancing operational performance. 2 figures, 1 table, and 14 references