OBJECTIVES: The objective of this study is to project the number of nonelderly people who could gain coverage under the Patient Protection and Affordable Care Act (PPACA) for the period from 2014 through 2020 in the 13-county Houston-Galveston area region.  METHODS: The 2008 and 2009 American Community Survey (ACS) Public Use Microdata file data were used to obtain current county-level data on the uninsurance rate in the region, weighted by age, income, and citizenship status. The impact of PPACA was projected based on estimates of growth in the size of targeted populations in each county and the anticipated responses of those populations to the major provisions of PPACA. To project coverage with PPACA, participation rates (the percent of the eligible population likely to enroll in Medicaid or purchase private insurance in an exchange or elsewhere) were applied to the projected number of uninsured in applicable groups. The participation rates are informed assumptions based on the best evidence available from public and private insurance studies currently available in the literature.   RESULTS: We estimated county level projection in the 12-county Houston-Galveston region. The projections indicate that, if fully implemented, PPACA could cut the uninsurance rate in the region by half, from 26% in 2010 to 13% in 2020. This change translates into health insurance coverage for approximately 2 million additional people, from the current 4.2 million to a projected 5.9 million. The number of Medicaid enrollees could increase by an estimated 600,000 (a 79% increase), although private insurance coverage, which could increase by as much as 1 million enrollees (a 30% increase), will remain the primary source of coverage for most people. CONCLUSIONS: Coverage gains from PPACA will vary considerably by county, depending on the age-income-citizenship characteristics of the population, current uninsurance rates, and the rate of population growth.