INTRODUCTION: Hospital care for ambulatory care sensitive conditions (ACSC) is potentially avoidable and often viewed as an indicator of suboptimal primary care. However, potentially preventable encounters with the health care system also occur in emergency department (ED) settings. We examined ED visits to identify subpopulations with disproportionate use of EDs for ACSC care. METHODS: We analyzed data from the 2007-2009 National Hospital Ambulatory Medical Care Survey for 78,114 ED visits by adults aged 18 and older. Outcomes were ACSC visits determined from the primary ED diagnosis. We constructed analytic groups aligned with Agency for Healthcare Research and Quality's priority populations. Multivariate logistic regression was used to estimate the odds of all-cause, acute, and chronic ACSC visits. We used Stata SE survey techniques to account for the complex survey design. RESULTS: Overall, 8.4% of ED visits were for ACSC, representing over 8 million potentially avoidable ED visits annually. ACSC visits were more likely to result in hospitalization than non-ACSC visits (34.4% vs. 14.0%, P<0.001). Multivariate models revealed significant disparities in ACSC visits to the ED by race/ethnicity, insurance status, age group, and socioeconomic status, although patterns differed for acute and chronic ACSC. CONCLUSIONS: Disproportionately higher use of EDs for ACSC care exists for many priority populations and across a broader range of priority populations than previously documented. These differences constitute disparities in potentially avoidable ED visits for ACSC. To avoid exacerbating disparities, health policy efforts to minimize economic inefficiencies in health care delivery by limiting ED visits for ACSC should first address their determinants.