OBJECTIVE: Attempted suicide is the strongest known predictor of completed suicide. However, suicide risk declines over time after an attempt, and it is unclear how long the risk persists. Risk estimates are almost exclusively based on studies of less than 10 years of follow-up. METHOD: The authors followed a cohort of 100 consecutive self-poisoned patients in Helsinki in 1963, for whom forensically classified causes of death during the following 37 years were investigated. RESULTS: They found that suicides continued to accumulate almost four decades after the index suicide attempt. CONCLUSIONS: A history of a suicide attempt by self-poisoning indicates suicide risk over the entire adult lifetime.