Treatment with cytotoxic chemotherapy and radiotherapy is associated with significant gonadal damage in men and women. The likelihood of gonadal failure following cytotoxic chemotherapy is dependent on the drug and dose, and in women there is also an effect of age at treatment. Irradiation of the testes or ovaries, either directly or indirectly, is also a significant cause of gonadal dysfunction, and the potential to recover from damage is clearly related to the radiation dose received. Several methods of preserving gonadal function during potentially sterilizing treatment have been considered. At present, sperm banking remains the only proven method in men, although hormonal manipulation to enhance recovery of spermatogenesis and cryopreservation of testicular germ cells are possibilities for the future. Transposition of the ovaries to allow better shielding during radiotherapy is of use in some women, and the prospect of cryopreservation and reimplanation of ovarian tissue appears to be promising.