During the period September 1981 to August 1985, we investigated every reported case of measles in Oklahoma to confirm the diagnosis, to determine the source, and to identify contacts to prevent spread of the disease. During this time, 33 serologically and/or epidemiologically confirmed cases were investigated. Nine (27%) persons acquired measles in a medical office or clinic waiting area. Eight of these recalled direct face-to-face contact with a source. An additional six (18%) cases were associated with exposure to these medically acquired cases, for a total of 45% that were the direct or indirect result of exposures in medical waiting rooms. The medical waiting room is a location where a reservoir of susceptible individuals may congregate, allowing for potential exposures to measles and other infectious diseases. Because many persons in these settings are too young to have received routine measles vaccination, other measures to decrease exposures in this setting may be necessary to achieve the goal of measles elimination in the United States.