The importance of human genetics in the work of William Bateson (1861-1926) and in his promotion of Mendelism in the decade following the 1900 rediscovery of Mendel's work is described. Bateson had close contacts with clinicians interested in inherited disorders, notably Archibald Garrod, to whom he suggested the recessive inheritance of alkaptonuria, and the ophthalmologist Edward Nettleship, and he lectured extensively to medical groups. Bateson's views on human inheritance were far sighted and cautious. Not only should he be regarded as one of the founders of human genetics, but human genetics itself should be seen as a key element of the foundations of mendelian inheritance, not simply a later development from knowledge gained by study of other species.