The spectrum of illness and use patterns of 540 elderly patients (greater than or equal to 65 years) admitted to an emergency department (ED) were compared to an equal number of nonelderly patients. The proportion of visits by the elderly group to the ED was similar to the proportion of elderly residents in the area surrounding the hospital. Elderly patients were more likely than nonelderly patients to have an emergent diagnosis (34.4 vs. 8.3%), to arrive by ambulance (54.6 vs. 23.5%), to be admitted to the hospital (51.1 vs. 14.4%), and to have a medical (as opposed to a surgical) illness (75.0 vs. 53.2%). The spectrum of diseases was different between the two groups. Elderly patients had a higher proportion of cardiac (28.4 vs. 7.2%) and pulmonary disease (5.3 vs. 2.8%). Nonelderly patients had more injuries (30.5 vs. 10.7%) and self-limited infectious disease (11.5 vs. 5.0%). The proportion of psychiatric disease and social problems was low in both groups, about 5%. Elderly patients had a significantly lower proportion of nonurgent diagnoses (19.4 vs. 32.0%) than the nonelderly patients. Use of the ED by elderly patients is different from nonelderly patients in that they are more likely to have a serious medical illness. There is little evidence that elderly persons use the ED for primary self-care or social problems.