BACKGROUND: All prisoners' suicides in Finland during 1969-1992 (n = 184) were studied. METHOD: The data were collected from official documents. RESULTS: Of all prisoners' deaths, 47% were suicides. The rate of suicide among male prisoners was three-fold compared to the normal adult Finnish male population. More than half of those committing suicide had a psychiatric disturbance and one half of them had visited the prison health services because of a psychiatric problem not more than one week before the suicide. Almost one third of the suicides were committed in isolation rooms. Contrary to the findings of many previous studies, there was no concentration of suicides at weekends, on religious holidays, in different seasons nor at the beginning of the confinement. CONCLUSIONS: The most important finding of this study was the common use of health care facilities in the prison just before the suicide. It is important to try to develop the means to recognize suicidal ideation among all prisoners seeking psychiatric care. The surveillance of prisoners in isolation cells needs to tighten up and should probably be continuous.