- The prevalence of suicidal ideation/behavior in 1983 or 1987 and its association with future mental health in 2001 were evaluated in a provincially representative sample of Canadian adolescents (n = 1,248) aged 12 to 16 years. Approximately 13.3% (95% CI = 11.5-15.3) of adolescents self-reported suicidal ideation/behavior. Adolescent agreement with parent (κ = .07) and teacher (κ = .05) reports at baseline was low because adults identified so few subjects. In adulthood, the associations between adolescent self-reports of suicidal behavior/ideation and major depression and other mental health indicators were explained by respondent sex and adolescent emotional problems reported in 1983/1987. Adolescents with suicidal behavior/ideation often are not recognized by their parents and teachers and may be at risk for persistent psychiatric problems attributable to coexisting mental health problems early-on.