The excellent and balanced article by Jadoul et al., in this issue of HRU, reviews the available evidence for fertility preservation in girls and young women at risk of a premature menopause. Importantly, they also present their own experience of ovarian cryopreservation in 58 cases all under 16 years old. To date there have been at least 10 pregnancies worldwide after othotopic reimplantation of frozen–thawed ovarian cortex. The success rate is unclear as the denominator (the number of women in whom frozen–thawed ovarian tissue has been reimplanted) is unknown. There have been no pregnancies reported following the reimplantation of ovarian tissue harvested pre-pubertally, but with the accepted age-related decline from birth in the number of non-growing follicles, young children are potentially ideal candidates for this procedure (Wallace and Kelsey, 2010). Jadoul et al. demonstrate that it is safe and feasible to collect ovarian tissue for freezing, laparoscopically under a general anaesthetic, without complications and without delaying cancer chemotherapy. However, their case series clearly demonstrates the difficulty of giving an accurate prognosis for fertility before treatment starts, for this may change as the disease and therapeutic requirements evolve. Patients classified initially as low risk for a premature menopause (Wallace et al., 2005a) may become high risk later if they relapse. Acute lymphoblastic leukaemia is the commonest childhood malignancy with around 80% of patients becoming long-term survivors. First-line treatment of these patients is associated with an excellent prognosis for future fertility. Not only will the survivors of first-line therapy be able to have their own children naturally, but their offspring also are not at increased risk of congenital abnormalities or cancer in childhood. However, those patients who relapse after first-line treatment may require conditioning treatment with total body irradiation (TBI) and myeloablative chemotherapy, and a bone marrow transplant from an HLA-matched donor. TBI is likely to be sterilizing (Wallace et al., 2005b), and in children will affect uterine development