To identify potentially preventable mortality other than suicide among psychiatric emergency room patients, the authors compared the rates of accidental and homicidal death among 5,284 consecutive psychiatric emergency room patients with those expected for an age-, sex-, and race-matched sample of the general population. The rate of accidental death was two and one-half times and the rate of homicidal death nearly twice the expected rate for the matched general population. Diagnostic and demographic analyses indicated that increased risk of death from either cause was highest among alcoholics, schizophrenic patients, and males. The implications of the findings for clinical care are discussed.