Psychiatric morbidity was studied in 73 patients of three Units (Medicine, Surgery and Obstetrics) of a general hospital (S. Francisco Xavier Hospital, Lisbon). In the first stage, the patients were clinically evaluated by their doctors. In the second stage, psychiatrists using the General Health Questionnaire (G.H.Q. 30) interviewed all the patients according to the clinical evaluation, 41% of the patients had a significant psychological disorder. However, very significant differences were found between the prevalence rates in the three units. As defined by the G.H.Q. 30, 50 patients (68.5%) had psychiatric disorders, which is statistically different from the results obtained through clinical evaluation. The depression and anxiety syndromes were the most frequent disorders. Organic mental disorders were less frequent and almost limited to medical patients. The results of this study confirm a high rate of psychiatric morbidity in the general hospital, although considerable differences exist between the three units included in the study. We can also conclude that many psychiatric disorders are not correctly identified. This fact, more frequent in units where there is a more brief doctor-patient relationship, supports the necessity of implementing liaison psychiatry programs.