A previous paper in this series with the same title (Lipowski, 1979) described the history and recent developments in the organisation of consultation liaison psychiatry. I therefore cover two other aspects, the nature of the psychological reactions to physical illness and the clinical role of the psychiatrist working on general surgical and medical wards. Lipowski remarked on the “generally mediocre quality of research” and on the lack of a “single fully adequate textbook”. These deficiencies remain all too apparent and the increasingly large literature is still mainly “clinical and anecdotal”. However straightforward clinical descriptions do provide an essential background to understanding the practical impact on patients' and families' lives of illnesses and of their treatment. A good knowledge of medicine is also essential and the liaison psychiatrist requires an up to date textbook and should try and read review papers and editorials in the general medical journals.