An extensive review of the use of non-human primates in contraceptive research was compiled in December 1971. An effort has been made to update certain topics from that symposium, specifically (1) similarities and differences between humans and other primates with respect to gametogenesis and gamete transport, implantation and ovum development, sexual cycles and sexual behaviour; (2) metabolism of steroids in nonhuman primates; (3) certain metabolic effects of steroids in non-human primates, canines, and humans; and, (4) the relevance of certain aspects of toxicity, such as tumorigenesis, when studied in non-human primates and other species.