Klinefelter’s Syndrome is a genetic disorder characterized by infertility, abnormal male breast tissue development (gynecomastia) and small, firm testes. It is the most common cause of azoospermia (no sperm production). Klinefelter’s Syndrome is caused by an abnormal number of sex chromosomes. Whereas a normal male genetic make-up includes one “X” chromosome and one “Y” chromosome, in patients with Klinefelter’s Syndrome, an extra “X” chromosome is present, resulting in three (XXY) sex chromosomes. Thought at one time to be hopelessly infertile, it has been found that these men can have small amounts of sperm production occuring within the testicle. Our Center has successfully recovered sperm in men with this disorder who have gone on to father normal, healthy children. It is important that all men with very low or absent sperm counts be tested for Klinefelter’s Syndrome before offering IVF and ICSI.