This paper points out some of the deficiencies in the conventional measures used to assess the impact of supply reduction efforts. In addition, it offers alternative approaches that promise to provide more insight into the effectiveness of such strategies. Conventional measures discussed include the organizational measures, e.g., quantifying supply reduction activities such as the number of drug-related arrests, the number of acres of marijuana destroyed, the number of smuggling vessels seized, and the retail prices of various drugs. The author argues that the results of using these measures, while providing a gauge of drug activity, are far from accurate. Alternatives offered include comparing current illicit drug prices to those that would prevail in a legalized drug market; determining the cost of a day-long binge using various drugs; distinguishing shifts in supply and the implications of equilibrium shifts; and determining the prices of various drugs at different stages of production and distribution to establish a trend that would help explain how price changes at a given stage affect prices at other stages. Recommendations include further research concerning the industrial organization of the drug industry and the dynamics of how supply is impacted by different types of enforcement. The analyses in this paper suggest that supply reduction efforts have occasionally been effective in substantially raising drug prices, thereby limiting consumption and abuse. These successes, however, are rare and qualified. Footnotes, tables