We conducted a retrospective review of the lactation experience of female survivors who received 24 Gy cranial radiotherapy as CNS prophylaxis for acute lymphoblastic leukemia in childhood prior to 1982 and who attend the Long-Term Follow-Up Clinic at Sydney Children's Hospital, Randwick, Australia. Median time since diagnosis is 28 years (range 25-37 years). Twelve have produced offspring. Ten report minimal or no breast changes during pregnancy and failure to lactate postpartum. All patients remain in remission. These data suggest a high risk of failure of lactation in women treated during childhood with 24 Gy cranial irradiation. Awareness of this possibility can assist in counseling.