INTRODUCTION: Self-poisoning is a risk factor for premature death and for suicide, but for how long? The aims were to examine the mortality rate, causes of death, and risk factors for mortality and suicide during 20 years. METHOD: Prospective cohort study including all patients discharged after self-poisoning from all medical departments in Oslo in 1980 (n = 946, 51 % females, median age 31 years). Standardized mortality ratios (SMRs) and Cox regression analysis were used. RESULTS: During follow-up, 355 (37.5%) of the patients died, SMR 4.6 (95% CI, 4.2-5.1). After 15 years, the SMR was still 3.3 (95% C.I., 2.5-4.2). Sixty-seven (7.1%) committed suicide, SMR 26.7 (95% CI, 21.0-33.9). The risk of death from all causes was significantly higher. Unspecific risk factors for death were found. A suicidal motive was the only risk factor for suicide. CONCLUSION: The mortality rate implies a poor prognosis in this patient group.