Two-stage screening for psychiatric disorder was carried out with a sample of 99 male and 95 female outpatients with insulin-dependent diabetes mellitus, using the General Health Questionnaire and the Clinical Interview Schedule. The estimated prevalence of psychiatric disorder in this sample was 18%: only 28% of the psychiatric morbidity so identified was detected by physicians. In contrast, physicians rated 10% of the sample as psychiatric 'cases' using a simple 6-point scale.