Data were obtained from the System To Retrieve Information From Drug Evidence (STRIDE) of the Drug Enforcement Administration. For each drug, figures showed estimated prices at several hypothetical distribution levels set by the analysis team to enhance the reader's ability to compare prices as drugs moved from wholesale to retail levels. Since 1995 the retail price for cocaine has ranged between $100 and $150 per pure gram. There have been sharp "spikes" in prices, which appear to correlate with interdiction events. Heroin prices have fallen at all distribution levels for nearly two decades. Heroin injection drug users have experienced a relatively modest decrease in heroin prices. For them, heroin cost approximately $3.00 to $3.60 per pure milligram in the early 1980's and $1.80 to $2.10 per pure milligram in the late 1990's. For methamphetamine, prices for the lowest-level sales (estimated at the typical purchase of three pure grams - about seven bulk grams at 41-percent purity) were approximately $300 in the early 1980's and $160 in the late 1990's. Many marijuana users buy the drug in ounce bundles, so prices estimated for this level probably represent retail-level purchases, albeit relatively large ones. A purchase at the ounce level probably cost about $150 in the late 1990's, compared with $80 in the early 1980's. The report concludes that supply-based enforcement programs have been remarkably successful at keeping illicit drug prices at very high levels, but not so successful at pushing them higher during the 1990's. If demand-based efforts can reduce the market for illicit substances, especially among hardcore users who appear to provide most of the demand, then future drug prices could decline as suppliers seek to sell to fewer buyers; however, the prevalence of hardcore drug use has not declined much since the early 1990's, so decreased demand is an unlikely explanation of past trends. 9 figures, 9 tables, and appended extensive supplementary tables