PIP: This large literature review of gonadal function and reproduction in men and women attempts to synthesize the material presented rather than enumerate bibliography. Topics covered include: 1) signals important in gonadal function regulation (cyclic adenosine monophosphate, luteinizing hormone [LH], follicle stimulating hormone [FSH], and various steroids) and various feedback mechanisms these agents trigger; 2) particular properties of gonadotropic hormones (biological and chemical separability of FSH and LH); 3) purification and characterization of gonadotropins (including assay procedures and tables of standard values); 4) the mechanism of ovulation; 5) luteal tissue formation, maintenance, and termination of function; 6) pituitary--gonadal relationships; 7) steroid receptors; and 8) the relationship of the central nervous system to control of pituitary FSH, LH, and prolactin secretion. Neurotransmitters, circadian rhythms, stress, and brain functions are discussed in terms of their roles in central nervous system mediation of gonadal function and reproduction.