OBJECTIVE: To explore trends in the nonelderly uninsured population between 1987 and 1996 and examine whether the broad disparities in medical care utilization and out-of -pocket spending between the privately insured and uninsured populations that existed in 1987 continued over the following decade. DATA SOURCES/STUDY DESIGN: Data are from the 1996 Medical Expenditure Panel Survey and the 1987 National Medical Expenditure Survey. We used survey data to create descriptive tables examining the characteristics of the uninsured population and the use of medical services, total and out-of -pocket expenditures, and the burden of out-of -pocket spending for the uninsured and the privately insured in 1987 and 1996. Tabulations are presented by demographic and socioeconomic characteristics. PRINCIPAL FINDINGS: The composition of the uninsured population changed somewhat between 1987 and 1996, with adults over age 18 and employed persons making up larger proportions of the uninsured in 1996, and the poor and those in fair or poor health making up smaller proportions. There were few changes in utilization of services by the uninsured over this period and no change in mean expenses, but there was an increase in receipt of at least one preventive service (mammograms) and a decline in the proportion of families with high out-of-pocket burden. Disparities in use and expenses that existed between the uninsured and the privately insured in 1987, however, remained in 1996. CONCLUSIONS: Despite the fundamental changes in the health care system that took place between 1987 and 1996, health care utilization and expenses for the uninsured changed very little. The uninsured are still much less likely to use services than are the privately insured, and they pay for a larger proportion of their medical care expenses out of pocket. There was some improvement in the burden of out-of -pocket spending between 1987 and 1996, but a significant number of the uninsured still have high financial burden.