This report presents information from the 2000 National Household Survey on Drug Abuse (NHSDA) on the number and percentage of the population in the nation and in each state who need but did not receive treatment for an illicit drug use problem, referred to as the treatment gap. Following the introduction, chapter 2 presents national estimates of the need for treatment and the treatment gap. Overall treatment need and treatment gap estimates are discussed first, followed by discussion of treatment need estimates arranged by age, gender, race/ethnicity, geographic area, education, and employment. Chapter 3 focuses on state treatment gap estimates and includes a summary of the methodology used to calculate these estimates followed by the results and discussion. Two appendices also are included. Appendix A provides information on the measurement of dependence, abuse, treatment, and treatment need, and Appendix B provides technical details on the state estimation methodology. (Contains 10 references and 22 tables.) (GCP)