To examine the prevalence of psychiatric disorders in patients with long-standing type I diabetes mellitus, we assessed a series of candidates for pancreas transplantation. Using the Diagnostic Interview Schedule, six-month and lifetime prevalences of psychiatric disorders were established for the candidates and their potential donors (first-degree relatives). Excluding tobacco use disorder and psychosexual dysfunction, 38 diabetic subjects (51%) received one or more psychiatric diagnoses. The lifetime prevalence of major depression was comparable for female (11 of 48 [22.9%]) and male (seven of 27 [25.9%]) diabetics; both rates were significantly higher than rates in first-degree relatives and the general population. Among female diabetics, the six-month and lifetime prevalences of simple phobia were increased vs donors and the general population; among male diabetics, the lifetime prevalence of antisocial personality disorder was greater than that in the general population. None of these disorders was found to be related to the duration of diabetes or the presence of various complications. The data suggest that increased rates of psychiatric disorder in type I diabetics have both gender-independent and gender-related components.