Ambulatory medical care is the predominant method of providing health care services in the United States and occurs in a wide range of settings. The largest proportion of ambulatory medical care visits occurs in physician offices (80%), whereas approximately 9% of all ambulatory medical care visits in the United States occur in OPDs (1).This report presents the most current nationally representative data on OPD care in the United States. Information about OPD utilization during 2006 and selected trend data are presented. Data are from NHAMCS, the longest continuously running nationally representative survey of hospital ED and OPD utilization.