During the past decade, advances in cancer treatment have increased survival rates of both boys and men. However, cancer treatment itself can compromise fertility, especially exposure to alkylating agents and whole body irradiation, which cause substantial germ cell loss. Children and adolescents with testicular cancer, leukaemia, and Ewing sarcomas are at the highest risk of developing permanent sterility from cancer treatment. Consequently, various strategies to preserve fertility are necessary. Sperm cryopreservation is an effective but underused method to safeguard spermatozoa. In the past few years, large advances have been made in prepubertal germ cell storage aimed at subsequent transplantation of testicular tissue and associated stem cells. Although still experimental, these approaches offer hope to many men in whom germ cell loss is associated with sterility. The derivation of male gametes from stem cells also holds much promise; however, data are only available in animals, and the use of this method in human beings is probably many years away.