The principles of treating cancer in a pregnant woman should be the same as for a nonpregnant woman but the timing of the treatment may be influenced by the natural history of the cancer and its prognosis, and the stage of the pregnancy. The radiation dose to the fetus depends on a number of factors, including the type of machine, prescribed dose, and anatomical area to be treated and the gestational age of the fetus. The management of early-stage Hodgkin's disease involves chemotherapy and involved-field radiotherapy rather than the larger 'mantle' radiotherapy fields, and hence the risk to the fetus from modern treatment should be considerably less. Current studies are investigating the role of dose-dense neoadjuvant chemotherapy before definitive chemoradiation in nonpregnant women with locally advanced cervical cancer. Brain tumours, and head and neck cancers are much less frequently encountered in pregnancy but in general would require radiotherapy without delay.