James Crow has not only been a central figure in the history of twentieth century evolutionary genetics, but also has done a great deal of service for the sciences, as a teacher and mentor to some of the most influential biologists today, and as a leader in professional and public scientific societies. His research covered speciation, genetic load, the theory of random drift, the effects of inbreeding, the evolution of sex and effects of atomic radiation in human populations. Crow served as President of the Genetics Society of America and the American Society of Human Genetics, and is a member of the National Academy of Sciences, the National Academy of Medicine and the American Academy of Arts and Sciences. His work has shaped the thinking of generations of evolutionary biologists and geneticists.