Left testicular growth arrest (hypotrophy) is seen in association with the varicocele. The mechanism responsible for the growth arrest is undefined. It most likely represents a combination of effects related to thermoregulation, temperature dependent enzyme systems, intratesticular hormonal concentrations, and alterations in paracrine interactions involved in spermatogenesis. All of these theories are based on the assumption that the varicocele is associated with an abnormality of blood flow. Growth arrest is reversible and catch-up growth of the left testis occurs after surgical correction of the varicocele. The relationship of testicular hypotrophy and its reversibility to subsequent fertility is unknown; however, clinical studies suggest that the improved growth of the testis, increase in total sperm counts, and improvement in other seminal parameters will be beneficial to ultimate fertility. The best clinical indication of significant testicular dysfunction related to the varicocele is growth arrest. The measurement of a 2 mL or greater size discrepancy between the left and right testis in the adolescent constitutes significant growth arrest in the left testis and is the main indication for surgery in the adolescent. Measuring testicular volume is most accurately performed with ultrasound. A decrease in testicular growth by two standard deviations from growth curves, scrotal pain, or a large (Grade 3) varicocele are other reasons to consider varicocele repair. Despite claims of a higher persistence rate in adolescents than adults after surgery, our review suggests similar persistence rates of 15% when a retroperitoneal approach to repair is used. At present, the procedure with the reported lowest persistence rates (1% to 2%) in adolescents is the high retroperitoneal ligation of the testicular artery and vein. The effects of internal spermatic artery ligation on spermatogenesis are unknown. The microsurgical inguinal or subinguinal approach with its low rate of hydrocele formation and low persistence rate deserves to be considered and used by pediatric urologists. The objectives of promoting testicular growth and possibly improving fertility later in life must take into consideration the psychological impact of these issues on the adolescent.