The author states that homicide is a relatively rare event in Canada & there is no evidence that homicidal deaths have increased from 1957-1967 (rate: 1.5/100,000). Data from 93 patients committed to Ontario hospitals as the result of violence–homicide, attempted murder, infanticide, rape-indicates powerful warning signals were present & their acts of violence may have been prevented. Current attempts to develop predictive measures of danger are examined. (50 ref)