Abstract. Objectives: To determine how the demographic, clinical, and utilization characteristics of emergency department (ED) frequent users differ from those of other ED patients. Methods: A cross-sectional and retrospective cohort study was performed using a database of all 348,858 visits to the San Francisco General Hospital ED during a five-year period (July 1, 1993, to June 30, 1998). A “frequent user” visited the ED five or more times in a 12-month period. Results: Frequent users constituted 3.9% of ED patients but accounted for 20.5% of ED visits. The relative risk (RR) of frequent use was high among patients who were homeless (RR = 4.5), African American (RR = 1.8), and Medi-Cal sponsored (RR = 2.1). Frequent users were more likely to be seen for alcohol withdrawal (RR = 4.4), alcohol dependence (RR = 3.4), and alcohol intoxication (RR = 2.4). Frequent users were also more likely to visit for exacerbations of chronic conditions, including sickle cell anemia (RR = 8.0), renal failure (RR = 3.6), and chronic obstructive pulmonary disease (RR = 3.3). They were less likely to visit for all forms of trauma (RR = 0.43). Survival analysis showed that only 38% of frequent users for one year remained frequent users the next year. However, 56% of frequent users for two consecutive years remained frequent users in the third year. Conclusions: Frequent use of the ED reflects the urban social problems of homelessness, poverty, alcohol abuse, and chronic illness. Frequent use of the ED shows a high rate of decline from one year to the next. This rate of decline slows after the first year and suggests the existence of a smaller group of chronic frequent users.