There have been no detailed descriptions of psychiatric patients who have died by suicide pact. We examined the social and clinical characteristics of pact cases in England and Wales using a national clinical survey sample of people who died by suicide pact and who had been in recent (<12 months) contact with mental health services. Over the study period (1996-2005), there were 278 cases of suicide who had died in a pact, 77 (28%) of whom had been in recent service contact. The most common cause of death overall was by carbon monoxide poisoning, but those in contact with services were more likely to use more violent methods compared with other pact victims. Nearly half (47%) had affective disorder and 68% had previously self-harmed. Over a quarter (29%) had died within 3 months of discharge from psychiatric care and 36% had missed their last service appointment. Pact cases were more likely than solitary suicide cases to have experienced recent adverse life events, typically family problems. Measures that may prevent suicide pacts in the mentally ill include the effective treatment of depression and closer supervision in both in-patient and community settings. Awareness of the family environment may contribute to reduced risk.