From time to time in the history of genetics there appear upon the scene problems which, once clearly defined, become a focus of interest not for genetics alone, but for many disciplines. Two examples in relatively recent times are the discovery of genetic recombination in bacteria and viruses, and the discovery of the Rh blood types. Bacterial recombination almost at once became of concern to the epidemiologist, the serologist, and the taxonomically inclined bacteriologist, as well as the geneticist. Likewise, the significance of the discovery of the Rh blood groups was at once apparent to the clinician, the serologist, and the anthropologist, in addition to the geneticist. The subject of our present article, the abnormal haemoglobins, would appear to be another of these problems which lie at the cross-roads of several disciplines, in this case biochemistry, clinical medicine, anthropology, and, of course, genetics. In contrast to the other problems referred to above, however, the developments in regard to the abnormal haemoglobins are so recent that our perspective at present is at best blurred. By tradition the Galton Lecture has been devoted to a definitive type of presentation. The time is not yet come for that type of presentation in the field under discussion in this paper. Accordingly, in addition to a brief summarization of some of the apparently established facts, I will emphasize some of the unsolved issues in this area, and the present state of our information concerning these issues. At the very outset, I would like to acknowledge the extent to which my own work and thinking in this field has profited from my associations with Dr