OBJECTIVE: To investigate the prevalence and correlates of suicidal behaviors among youth with insulin-dependent diabetes mellitus (IDDM) for up to 12 years after disease onset. METHOD: The occurrence of suicidal ideation and suicide attempts was assessed shortly after disease onset and repeatedly thereafter as part of a longitudinal study of diabetic children. Initial psychiatric status and symptomatology, characteristics of the medical illness, and sociodemographic variables were considered as potential correlates of suicidal behaviors. RESULTS: Young patients evidenced higher than expected rates of suicidal ideation, but relatively few attempted suicide over the follow-up. Among those who did attempt suicide, diabetes-related methods commonly were used. Suicidal ideation shortly after IDDM onset was related only to concurrent severity of depressive symptoms. Suicidal ideation over the follow-up was associated with later noncompliance with the medical regimen. CONCLUSIONS: Clinicians should be alert to the possibility of suicidal ideation among youth with IDDM because of the prevalence of those cognitions, the potential lethality of attempts due to insulin misuse, and the relationship of suicidal thoughts to later noncompliance with the medical regimen.