Since 1967 NIDA has provided the scientific community working on problems of drug abuse with authentic, standardized supplies of controlled research drugs and chemicals. These include marijuana cigarettes, known hallucinogens, heroin, amphetamines, cannabinoids, and many other drugs essential for both clinical and laboratory research studies. The number of drugs currently supplied has grown significantly because of increasing demand due to a combination of factors including increased regulatory requirements that tend to discourage commercial availability and rapidly expanding research efforts in the area of drug abuse. A diverse inventory of drugs is synthetically maintained with a simultaneous effort directed at the synthesis of new compounds. The stability of all compounds is constantly monitored to assure purity. Many of the drugs are synthesized and stocked to support preclinical studies in animals and are produced in quantities ranging up to several kilograms. Radiolabeled compounds are prepared in specific activities ranging up to 75 Ci/mmole if tritium- labeled and up to 300 Ci/mmole if iodine-125-labeled. The higher specific-activity compounds are used in receptor-binding studies and in radioimmunoassays. Lower activity compounds are used in metabolism studies and are usually specifically labeled to avoid metabolic "scrambling." A broad range of deuterium-labeled compounds are synthesized on a regular basis for use as standards in quantitation of drugs by mass-spectrometry. Since most of these drugs are Schedule I compounds, an extensive inventory and shipment tracking system is maintained on NIDA's computer system.