OBJECTIVES The purpose of this study is to determine the economic benefit, if any, of reducing waiting from the perspective of the Ontario health care system. METHODS An investigation in the Canadian scientific and economics literature was conducted to determine the costs of assessment, diagnosis, treatment and follow-up of patients receiving care for a local recurrence. The risks associated with having a local recurrence, metastatic disease and terminal disease were also determined from the literature. The resulting cost of treatment was weighted according to the risk of each health event, and by the associated risk of recurrence due to radiotherapy delay. RESULTS The cost of treating a recurrence, weighted according to risk of progression to more severe disease, was approximately $36,000 within the model. The associated incremental cost savings per week of waiting reduction was $72.49. Sensitivity analysis was conducted around the estimate. CONCLUSIONS The cost savings associated with avoiding one breast cancer recurrence is approximately $36,000 from the perspective of the health care system. Reducing waiting for radiotherapy by one week may save the health care system $72 per patient in downstream costs. In a health care system like Ontario's, which treats 2800 new breast cancer patients per year, this may represent a significant reduction in operation cost. These savings should be considered in context of how much resource investment is required to reduce waiting.