Summary.Southampton Medical School holds its major examination of basic knowledge after rather than before students enter their first clinical attachments. An interview survey investigated its educational effects, and found that students adopt one of four revision approaches. The most successful, not just in terms of examination grade but more particularly in students' subsequent ability to retrieve and use the knowledge gained, occurred when students related their preclinical revision to their clinical experiences. One of these approaches, an elaboration of knowledge, is considered to be essential for effective clinical thinking yet is probably rare elsewhere in medical education since it appears to be a consequence of a particular curricular arrangement. An explanation is given in terms of current thinking in cognitive psychology, and this challenges the theoretical assumptions on which other research in medical education has been uncritically based. Some implications for medical education and further research are discussed.