From July through September 1987, our emergency department registered 17,214 patients, of whom 569 (3%) returned within two days of initial registration. Cases were reviewed to identify factors associated with return visits. Patient-related factors were responsible for a majority of repeat visits (267 cases, 53%). Illness-related factors, particularly evolution of disease under close outpatient observation, prompted return in 68 cases (13%). An additional 60 patients (12%) returned with new problems unrelated to their initial presentation. Physician-related factors were the primary reason for return in 92 cases (18%). Problems with our public health-care system prompted return in 18 cases (4%). Eighty-seven returning patients (19%) required emergency hospitalization, including 28 discharged due to physician errors. Regular case review of short-term returns to the ED should be included in a comprehensive ED-based program of quality assurance.