Women with early stage breast cancer are increasingly being treated with both adjuvant chemotherapy and radiotherapy. The optimal sequence of these two treatment modalities is yet to be defined. It remains controversial whether delaying radiotherapy in order to deliver chemotherapy compromises local disease control and survival. Consequently, clinical practice in the UK is divided, with a number of different combination schedules being used in an effort to bring forward the start of radiotherapy. In practice, however, any benefit in local control must be balanced against a potential increase in toxicity. A review of the current literature on the effect of radiotherapy delay is presented, together with data on the toxicity of combined chemo-radiotherapy schedules and recent data from clinical trials designed to determine the optimal sequencing of chemotherapy and radiotherapy.