The reproductive system consists of the hypothalamic-pituitary unit, the gonads (testes or ovaries), the reproductive tract, and the external genitalia. The functions of the reproductive system are to produce and deliver gametes (spermatozoa or oocytes) for sexual reproduction, and produce hormones that regulate reproductive function and secondary sex characteristics. Abnormalities in the physiologic function affect the development and delivery of gametes, and potential fertility. Male infertility may be due to abnormalities of hormonal control, testicular function, or sperm transport or delivery. Female infertility can be divided into several categories: ovarian, tubal and peritoneal, uterine, cervical, and other. This book provides a comprehensive review of the reproductive physiology; emphasizing hormonal control, gamete production, fertilization, implantation, and embryonic development. By developing a clear understanding of what is normal, you will better understand the abnormalities affecting fertility and the mechanisms behind treatment.