School-age children were assessed longitudinally for up to 9 years, after the onset of their insulin-dependent diabetes mellitus (IDDM), to determine the time-dependent risk of the psychiatric diagnosis of noncompliance with medical treatment and to examine protective and risk factors. The cumulative risk for this diagnosis over the 9 years was .45. Noncompliance tended to emerge in middle adolescence and was found to be protracted. Social competence, self-esteem, and aspects of family functioning at IDDM onset and initial psychiatric status did not predict noncompliance. However, noncompliance was associated with having major psychiatric disorder later in the course of IDDM.