This study aimed to estimate the prevalence of mental disorder in offenders convicted of serious violence, examine their social and clinical characteristics, and compare them with patients convicted of homicide. We examined a national clinical survey of all people convicted of serious violence in England and Wales in 2004. Mental disorder was measured by contact with mental health services within 12 months of the offense. Of the 5,966 serious violent offenders, 293 (5%) had been in recent contact with mental health services. Personality disorder (63, 22%) and schizophrenia (55, 19%) were the most common diagnoses. Most had previous convictions for violence (168, 61%). Seventy-two (25%) patients were at high risk of violence and 34 (49%) were not subject to the Care Programme Approach. Compared with serious violence offenders, homicide offenders were more likely to have been patients (293, 5% vs. 65, 10%; p < .01). We conclude that patients were responsible for a small proportion of serious violent offenses; however, high-risk patients require closer supervision, and regular inquiry about changing delusional beliefs, thoughts of violence, and weapon carriage.