Data from the National Health Interview Survey reveal that 4.7 million or 15% of US adolescents aged 10 through 18 were uninsured in 1989. Among adolescents, 73% were privately insured, 10% were publicly insured, and 2% were both privately and publicly insured. Poor, near-poor, and minority adolescents were at the greatest risk for lack of health insurance coverage. Among adolescents without insurance, cost continued to be cited as the leading barrier to obtaining coverage. A comparison of 1989 National Health Interview Survey data with a previous analysis, in which 1984 data were used, revealed a 10% increase in the proportion of adolescents without insurance coverage. The increase in the proportion of uninsured adolescents was entirely attributable to an erosion of private health insurance coverage. No significant change occurred in the proportion of adolescents with coverage under public programs. Planned expansions of the federally and state-financed Medicaid programs will help to stem further increases in the size of the uninsured adolescent population. However, unless marked improvements occur in the private health insurance sector, progress will be limited.