Fifty in-patient suicides occurring in an English health region over the five-year period 1987-91 were identified from two data sources: the Regional Health Authority's records of untoward incident reports and coroners' records. An analysis of the quality of incident investigations conducted locally was carried out. The people who committed suicide were more often men, with a similar sex distribution in the study population to suicides in the community. Male in-patient suicides (mean age, 40 years) were younger than females (mean age 58 years). There was a high incidence of violent methods and around a third of the deaths occurred in the week after admission. More than half the deaths had occurred outside hospital. The health service's untoward incident reporting system seriously under-enumerated cases of in-patient suicide. Even when notifications were made, they appeared to be of variable quality and few demonstrated a comprehensive investigation and action plan.