A questionnaire was developed to elicit medical students' attitudes to psychiatry. All 94 second year clinical students at a London teaching hospital completed the instrument before and after an 8-week psychiatric clerkship. Although two-thirds of the sample had mixed feelings about psychiatry initially, by the end of the clerkship the students' general attitude to psychiatry had changed significantly in a favourable direction. Analysis of 18 specific attitudes to psychiatry revealed that the students' first responses showed anticipatory bias and lack of uniformity. Later, however, only two specific attitudes had changed significantly: more students agreed that ‘problems presented by psychiatric patients are often particularly interesting and challenging’, and more of them disagreed with the statement that ‘psychiatric patients, generally speaking, are not easy to like’. The sexes differed on one attitude; more males than females agreed that “psychiatry is too inexact; it seems to lack a proper scientific basis”. Finally, the proportion of students who considered the possibility of specializing in psychiatry rose from 6 to 17% during the clerkship. The students' reasons for or against such a career are discussed.