The Generalised Health Questionnaire and Standardised Psychiatric Interview were used to determine psychiatric morbidity among 126 patients consecutively admitted to a medical oncology unit. Senior house officers and nurses also rated anxiety and depression. 36 (29%) patients were psychiatrically ill and affective disorders (29, 23%) predominated. Psychiatric morbidity was associated with feeling moderately or severely physically ill, and previous psychiatric illness, but not with awareness of having cancer or lack of a confiding tie. The General Health Questionnaire identified 79% of affective disorders at the cost of a 34% false positive rate. Doctors and nurses recognised only 49% of the depressed group; more of those with morbid anxiety (79%) were identified but only because they assumed most patients were anxious. Training in interviewing skills could substantially improve the identification and referral rates of patients with psychiatric morbidity.