OBJECTIVES: Evaluate the budget impact of substituting the current recommendation of the Colombian National Cancer Institute (CNCI) for the early detection of breast cancer in Colombia for an organized screening program based on annual mammography for women 40-69 years (OgSP). METHODS: A previous cost-effectiveness study funded by the CNCI showed that the OgSP was more effective but more expensive than the current recommendation of the CNCI, opportunistic screening based on biennial mammography for women 50-69 years and annual breast clinical exam for women 30-69 years (OpSP). A spreadsheet model following the ISPOR task force recommendations was developed to compute the annual, average, total, per-member-per-month (PMPM) and per-treated-member-per-month (PTMPM) costs and budget impact of the OgSP in four years. All inputs were based on local information and included Colombian population growth, age and gender distributions, breast cancer incidence rates in Colombian women and number of women eligible for breast cancer screening; mammography and clinical exam specificity, sensitivity and costs; opportunistic and organized program coverage and costs, and diagnosis confirmation exams and breast cancer treatment costs.  RESULTS: Total cost PTMPM was estimated to be $121 for the OpSP. With the new proportional share, it would increase to $241, a 99% increase. 98% of the costs came from the greater number of mammograms given the nature of the OgSP, and the greater number diagnosis confirmation exams and treated women given the major effectiveness of the OgSP in breast cancer detection. Results remained favorable for OpSP under all sensitivity analyses. CONCLUSIONS: The impact of substituting the current OpSP for the OgSP will yield very high costs to the Colombian health care system budget. Decision makers should consider other strategies for the early detection of breast cancer screening, more effective than the current OpSP and affordable, using the developed model to evaluate the budget impact of the new streategies under consideration.