When synthetic GnRH first became available for clinical study, there was not yet an adequate understanding of the physiology of GnRH secretion in the human to support its potential therapeutic application. As a result, early attempts at ovulation induction were unsuccessful. It was soon appreciated that an episodic mode of delivery was essential for normal pituitary stimulation by GnRH. Studies by our group and others which defined the frequency of pulsatile GnRH secretion in normal women at different stages of the menstrual were then key to designing a physiologic program of pulsatile GnRH administration that resulted in successful ovulation induction in patients with GnRH deficiency. Additional studies demonstrated that which replacement of GnRH using the subcutaneous route was adequate to reproduce normal physiology in GnRH-deficient men, the intravenous route was superior in women. We have now determined the dose of GnRH which is appropriate for the majority of women as 75 ng/kg, a dose which induces ovulation of a single dominant follicle, followed by normal luteal phase dynamics.