American adults frequently do not receive recommended health care. The extent to which the quality of health care varies among sociodemographic groups is unknown. We used data from medical records and telephone interviews of a random sample of people living in 12 communities to assess the quality of care received by those who had made at least one visit to a health care provider during the previous two years. We constructed aggregate scores from 439 indicators of the quality of care for 30 chronic and acute conditions and for disease prevention. We estimated the rates at which members of different sociodemographic subgroups received recommended care, with adjustment for the number of chronic and acute conditions, use of health care services, and other sociodemographic characteristics. Overall, participants received 54.9 percent of recommended care. Even after adjustment, there was only moderate variation in quality-of-care scores among sociodemographic subgroups. Women had higher overall scores than men (56.6 percent vs. 52.3 percent, P<0.001), and participants below the age of 31 years had higher scores than those over the age of 64 years (57.5 percent vs. 52.1 percent, P<0.001). Blacks (57.6 percent) and Hispanics (57.5 percent) had slightly higher scores than whites (54.1 percent, P<0.001 for both comparisons). Those with annual household incomes over 50,000 dollars had higher scores than those with incomes of less than 15,000 dollars (56.6 percent vs. 53.1 percent, P<0.001). The differences among sociodemographic subgroups in the observed quality of health care are small in comparison with the gap for each subgroup between observed and desirable quality of health care. Quality-improvement programs that focus solely on reducing disparities among sociodemographic subgroups may miss larger opportunities to improve care. Copyright 2006 Massachusetts Medical Society.