It would be difficult to think of a more important field of study in medicine than the interaction of cells with natural and foreign surfaces, but it is rare for those in the practice of medicine and surgery to get together with the basic scientists to discuss what they know about it, so that ground of common interest can be explored. Perhaps the symposium should have been entitled "Interactions between those interested in cell surfaces ••• " because it is here that the chief value of such meetings must lie. Even a brief perusal of this volume shows just how far advanced thought and work are on some facets of the topic. Some of the most pressing problems in medicine are those of tumour spread and of thrombosis of blood vessels where surface phenomena are of paramount importance. Our understanding is still very limited but, as the symposium illustrated, the answers are only to be found by study at fundamental levels, the work gaining direction and point from interaction with surgeons and others concerned with the actual disease states.