At the present time approximately 1 in 1000 young people aged between 16 and 35 years will have been cured of cancer in childhood and some of the treatment regimens used will have predictable effects on their future fertility prospects. In young women who have been exposed to radiotherapy below the diaphragm, the reproductive problems include the risk of ovarian failure and significantly impaired development of the uterus. The magnitude of the risk is related to the radiation field, total dose and fractionation schedule. Premature labour and low birth weight infants have been reported after flank abdominal radiotherapy. Female long-term survivors treated with total body irradiation and marrow transplantation are also at risk of ovarian follicular depletion and impaired uterine growth and blood flow, and of early pregnancy loss and premature labour if pregnancy is achieved. Despite standard oestrogen replacement, the uterus of these young girls is often reduced to 40% of normal adult size. Uterine volume correlates with the age at which radiation was received. Regrettably, it is likely that radiation damage to the uterine musculature and vasculature adversely affects prospects for pregnancy in these women. It has been demonstrated that, in women treated with total body irradiation, sex steroid replacement in physiological doses significantly increases uterine volume and endometrial thickness, as well as re-establishing uterine blood flow. However, it is not known whether standard regimens of oestrogen replacement therapy are sufficient to facilitate uterine growth in adolescent women treated with total body irradiation in childhood. Even if the uterus is able to respond to exogenous sex steroid stimulation, and appropriate assisted reproductive technologies are available, a successful pregnancy outcome is by no means ensured. The uterine factor remains a concern and women who are survivors of childhood cancer and their carers must recognize that these pregnancies will be at high risk.