Joseph Adams was eclectic in his interests and wrote on a variety of medical subjects. His last book published in 1814 was on hereditary disease and based on a lifetime's careful clinical observations. In it he distinguished between what would now be defined as dominant and recessive disorders; defined the term congenital; emphasised the role of inbreeding in producing clustering of certain inherited disorders; introduced concepts now known as founder effect, incomplete penetrance, and variable age at onset; emphasised the importance of environmental factors in precipitating disease in certain genetic disorders; and, finally, recommended the establishment of registers for the purpose of preventing genetic disease. But because he proposed no scientific explanation for these various ideas, they were largely ignored by his contemporaries. Nevertheless, it would seem right to regard Joseph Adams as perhaps the first clinical geneticist.