The optimal sequencing and timing of radiation and chemotherapy for patients with early-stage breast cancer are unknown, both with regard to each other and to surgery. Although intuitively it seems prudent to start both radiotherapy and combination chemotherapy as soon as possible following surgery, there is little information to suggest that reasonably short delays (up to a few months, perhaps) are deleterious. Study results do not suggest that concurrent chemoradiotherapy produces any substantial advantage in local control rates, compared with sequential treatment. However, the available data are very limited, and no randomized studies have been performed. Because of its theoretical advantages, concurrent chemoradiotherapy remains an approach worthy of further investigation, but the potential toxicity of such regimens makes careful study design imperative. At present, the effectiveness of chemotherapy does not appear to be impaired significantly by a 2- to 3-month break in therapy imposed by split-course combined-modality regimens.