Current variability in superovulatory response prevents the economical production of large numbers of high quality embryos and limits the use of embryo transfer. Pulsatile administration of GnRH (gonadotrophin releasing hormone) elicits pulsatile secretion of LH (luteinising hormone) while chronic treatment with a potent GnRH agonist reduces LH secretion. Using the latter, gonadotrophin-dependent preovulatory antral follicle development may be suppressed, resulting in a uniform cohort of small antral follicles in the absence of a dominant follicle which could then be superstimulated by exogenous gonadotrophin.