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Recent meta-analyses have shown the importance of locoregional control as a long-term determinant of breast cancer survival. Whether factors related to the delivery of radiotherapy, such as delay, dose, fractionation or irradiated volume, are associated with outcome remains unclear. We performed a critical review of the literature on delay to radiation using a computerized search of papers published between 1985 and 2000. Periods of accrual, details of radiotherapy, surgical and systemic treatment, and information on prognostic factors were noted. Studies on sequencing of adjuvant therapy were compared to studies on delay to radiation, classified according to whether or not patients also received chemotherapy. Comparisons of patients receiving systemic therapy to individuals spared this option were considered uninformative since the impact of delaying radiation is then highly confounded by systemic treatment received. The single published experimental study on sequencing suggests that delay to radiation may compromise local control, and this is consistent with a few retrospective reports on delay to radiotherapy among patients receiving chemotherapy. However, indirect evidence from two randomized clinical trials of chemotherapy, and the majority of observational studies on delay to radiotherapy, suggest that it has no impact on either local, distant control or survival. Factors, methodological, and others, that could explain these inconsistencies are discussed. No study restricted to patients at low risk of recurrence suggested an impact of delaying radiation. Short chemotherapy regimens are likely to represent a safe option with respect to outcome of radiation treatment.