Retail store-based health clinics, which provide basic preventive services and diagnose and treat simple health ailments, have proliferated rapidly in recent years. Younger families and people that have difficulty accessing health care services—including the uninsured and minorities—are among the groups most likely to use these clinics. Still, in 2007, only 1.2 percent of U.S. families reported they had visited a retail clinic during the past 12 months, and only 2.3 percent of families reported ever having visited one, according to the Health Tracking Household Survey conducted by the Center for Studying Health System Change. The boom in retail clinics, moreover, appears to be slowing. Continued fall-off in the growth of retail clinics would likely disproportionately affect underserved Americans who lack affordable alternatives for primary care.