OBJECTIVES: We examined the prevalence and correlates of substance use, dependence, and service utilization among uninsured persons aged 12 to 64 years. METHODS: We drew study data from the 1998 National Household Survey on Drug Abuse. RESULTS: An estimated 80% of uninsured nonelderly persons reported being uninsured for more than 6 months in the prior year. Only 9% of these uninsured persons who were dependent on alcohol or drugs had received any substance abuse service in the past year. Non-Hispanic Whites were an estimated 3 times more likely than Blacks to receive substance abuse services. CONCLUSIONS: Compared with the privately insured, uninsured persons had increased odds of having alcohol/drug dependence and appeared to face substantial barriers to health services for substance use problems.