The estimates presented in this article were derived from definitions and statistical estimating methods applied to the National Household Survey on Drug Abuse. However, this study applied more comprehensive selection criteria to identify need and new criteria for abuse, defined to include specific drug abuse behavior, e.g., frequency of drug use, injection drugs, and treatment participation. The article includes two separate estimates (based on severity) of people needing treatment, a combined total of 7.1 million people. The analysis presents improved estimates of the need for treatment at the national level; it does not explore the reasons for a gap between need for and supply of treatment. Policy decisions on resolving the treatment gap should depend on treatment effectiveness, i.e., treatment must make a difference in patient outcome if more resources are to be used to expand or enhance treatment capacity. This analysis shows that, even if treatment were completely effective, there would still be a problem of access to such services. Notes, tables, figure, references