Study objectives: To determine the frequency of, and patient population requiring, involuntary treatment orders in the emergency department. Design: Retrospective review of all patients requiring involuntary treatment orders during a one-month study period. Setting: An urban, university hospital, adult emergency department with 45,000 annual patient visits. Results: Three hundred fourteen of 3,637 patients (8.5%) required involuntary treatment orders. Orders used were observation and detention (57%), seclusion only (9%), restraint only (26%), or seclusion plus restraint (7%). Forty-six percent of patients arrived through the emergency medical services system; the remainder were brought by police or family or were self-referred. More patients required these interventions on the second shift. Most detained and secluded patients had psychiatric diagnoses and dispositions, whereas 100% of restrained patients had medical or surgical diagnoses, and nearly 50% required medical or surgical admissions. Conclusion: The frequent need for involuntary treatment orders for patients in an urban ED is reported. The patient population described, especially among restrained patients, differs significantly from those of studies performed in psychiatric settings. Legal doctrines pertinent to involuntary treatment are reviewed.