The effectiveness of specialised work in any branch of medicine cannot depend alone on the personal and professional qualities of the entrant into the field. It demands extended and systematic training, not only in the clinical speciality itself, but also in those many disciplines that bear upon it. In the course of his or her studies, the trainee psychiatrist is expected to further his acquaintance with the relevant basic medical sciences (especially neuroscience), and with organic medicine (particularly neurology), and with the application of these to his field of study. His understanding of these and many other subjects, including genetics, biochemistry, sociology, epidemiology, and statistics, is indispensable to his professional development. Extended clinical experience will teach him something of the day-to-day applications of these studies to psychiatric practice in a wide variety of circumstances. He may also acquire knowledge of such specialised areas of work as mental retardation and forensic psychiatry. Although he will be aware of his many limitations, the well-trained consultant will draw, in his general clinical practice, upon these various fields of knowledge with a justifiable measure of confidence.