Guidelines adopted in 1982 by the American College of Emergency Physicians were used to determine appropriate and inappropriate emergency department (ED) utilization patterns at three community hospitals during a two-week period in August 1983. In all, 3,130 visits were examined. There was an overall inappropriate visit rate of 10.8%, although considerable variation was observed among the three hospitals. Subgroups with the highest inappropriate visit rates included the following: 1) persons with Medicaid as the primary payment source (17.3%); 2) children aged 5 years or younger (15.2%); 3) those unable to identify a personal physician (14.1%); 4) unemployed persons (13.1%); 5) patients making visits during regular office hours (12.6%); and 6) those failing to attempt to contact their personal physicians (12.4%). These variations in inappropriate usage were all statistically significant at the P less than .05 level or better. Inability to identify a personal physician emerged as the most pervasive influence on inappropriate ED visit rates (P less than .001).