One goal of the Affordable Care Act is to improve patients' access to primary care and the coordination of that care. An important ingredient in achieving that goal is ensuring that patients have access to their primary care practice outside of regular business hours. This analysis of the 2010 Health Tracking Household Survey found that among people with a usual source of primary care, 40.2 percent reported that their practice offered extended hours, such as at night or on weekends. The analysis also found that one in five people who attempted after-hours contact with their primary care provider reported it was "very difficult" or "somewhat difficult" to reach a clinician. Those who reported less difficulty contacting a clinician after hours had significantly fewer emergency department visits (30.4 percent compared to 37.7 percent) and lower rates of unmet medical need (6.1 percent compared to 13.7 percent) than people who experienced more difficulty. The findings provide a valuable baseline on after-hours access, especially as patient-centered medical homes and accountable care organizations expand. Increasing support to primary care practices to offer or coordinate after-hours care may help reduce rates of emergency department use and unmet medical need.