The effects of gonadotropins on oocyte development are mediated through a variety of mechanisms, including production by granulosa cells of growth factors, cytokines, inhibins, activins, and steroids. Specific receptors for steroids, growth factors, and cytokines have been demonstrated on oocytes of several species. Gonadotropin modulation of follicular concentrations of these paracrine factors may ultimately be responsible for the precise regulation of oocyte function. As gonadotropin-releasing hormone antagonists and recombinant gonadotropins become available, the clinical use of more precise control of the endocrine, paracrine, and autocrine regulation of follicle growth and oocyte development can be more thoroughly investigated.