The successful treatment of childhood cancer can be associated with impaired gonadal function in adulthood. Chemotherapy and radiotherapy may damage germ-cell spermatogonia, resulting in impaired spermatogenesis or sterility in the male, or may hasten oocyte depletion with truncated fecundity and premature menopause in the female. The only established option in current clinical practice for preserving male fertility is cryopreservation of spermatozoa. The only strategy currently available for preserving female fertility is cryopreservation of embryos. Harvesting and storage of ovarian cortical tissue from girls and young women before potentially gonadotoxic chemotherapy has been available in a number of centres but there have been no live births and the procedure remains experimental. Standards for best practice in the cryopreservation of gonadal tissue, including the criteria for providing a service, patient identification and selection, standard operating procedures and requirements for safe storage, remain to be defined. Recent advances in assisted reproduction may circumvent natural conception barriers and the implications of impaired DNA integrity may be manifest as an increased risk of congenital abnormalities and chromosomal disorders in the offspring. In this chapter we consider the late reproductive sequelae following treatment for childhood cancer and options for fertility preservation. Copyright 2002 Elsevier Science Ltd.