Background: Cryptorchidism or undescended testis is the most common disorder of the male endocrine glands. The incidence of cryptorchidism is reported between 3.4% and 5.8% in full term boys and has been reported as high as 30% in premature boys. One third of boys with true cryptorchidism has bilaterally cryptorchid testes; while two-thirds are unilateral. Once cryptorchidism has been diagnosed, a plan of treatment should be developed. The main reasons advocated for treatment of cryptorchidism are increased infertility in unilateral and bilateral cryptorchid patients, increased testicular malignancy rate, and an increased risk of developing testicular torsion. The psychological stigmata of an empty scrotum are also of importance to both the patient and family. The current standard of therapy has been the surgical repositioning of the testis within the scrotal sac (orchidopexy). Infertility in adults who were previously cryptorchid boys is a subject of active research. Small descriptive studies report a 33% risk of infertility in previously unilateral cryptorchid males based on semen parameters compared to 7-10% of normal males with bilaterally descended testis. Other investigators have reported a severe stress pattern in the semen analysis of adult males who were previously cryptorchid. These data support the theory that despite early surgical intervention to position the testis within the scrotum, the testis may not regain its full fertility potential. Job and Baker have demonstrated that the cryptorchid testis never achieves its full fertility potential secondary to a central endocrinological dysfunction, a forme fruste of hypogonadotropic hypogonadism, in which the cryptorchid testis does not experience the characteristic gonadotropin surge of infancy. This has lead to the institution of a hormonal stimulation therapy in some European centers with a GnRH analog for a subset of males with unilateral biopsy proven impairment in germ cell counts of the cryptorchid testis. These observations are of great significance to the many boys who undergo early orchidopexy in the treatment of their undescended testicles only to suffer from impaired fertility as adults. The present clinical research project represents only objective #1 of a comprehensive study aimed at both evaluating the association between cryptorchidism in boys and impaired fertility in young men, assessing the effect of early hormonal intervention on this fertility potential. A separate research project for objective #2 will be made upon completion of data analysis of objective #1. The unique data bank actively maintained by the Divisions of Urology & Pathology at The Children's Hospital of Philadelphia of over 15 years of bilateral testis biopsy specimens on boys with surgically treated cryptorchidism will make this clinical research possible. This comprehensive study will be accomplished through two specific aims: 1. Objectively determining the frequency of impaired fertility and true infertility in the cryptorchid population treated with surgery alone. The outcome measures used will be post pubertal semen analysis and serum FSH, LH, testosterone, and inhibin B and the incidence of primary male factor infertility. 2. A future aim will be the development of an early hormonal intervention program for the cryptorchid population at risk for fertility problems based on testis biopsy. The short-term outcome measure will be evaluation of testicular histopathology and the long-term outcome measure will be parameters of the semen analysis.