This study estimated the possible surge in demand for primary care among the low-income population in Houston/Harris County under the Patient Protection and Affordable Care Act, and related it to existing supply by safety-net providers. A model of the demand for primary care visits was developed based on California Health Interview Survey data and applied to the Houston/Harris County population. The current supply of primary care visits by safety-net providers was determined by a local survey. Comparisons indicate that safety-net providers in Houston/Harris County are currently meeting about 30% of the demand for primary care visits by the low-income population, and the rest are either met by private practice physicians or are unmet. Demand for primary care by this population is projected to increase by 30% under health reform leading to a drop in demand met by safety-net providers to less than 25%.