OBJECTIVES: This incidence-based cost-of-illness analysis aims to quantify the costs associated with female breast cancer in Flanders for the year prior to diagnosis and for each of the five years following diagnosis. METHODS: A bottom-up analysis from the societal perspective included direct health care costs and indirect costs of productivity loss due to morbidity and premature mortality. A retrospective case-control study design compared total costs of breast cancer patients with costs of an equivalent standardised population with a view to calculating the additional costs that can be attributed to breast cancer. The sample was made up of women who had undergone surgical treatment for breast cancer and who were affiliated with the Christian Health Insurance Funds. Resource utilisation data were derived from national publications, the Christian Health Insurance Funds and statistical institutes. RESULTS: The sample consisted of 20,439 breast cancer patients. Total average costs of breast cancer amounted to €107,456 per patient over 6 years. Total costs consisted of productivity loss costs (89% of costs) and health care costs (11% of costs). Health care costs did not vary with age at diagnosis. Health care costs of breast cancer patients converged with those of the general population at five years following diagnosis. Patients with advanced breast cancer stadia had higher health care costs. CONCLUSIONS: To reduce costs associated with breast cancer, attention needs to be focused on decreasing the productivity loss from breast cancer. The implementation of new techniques to prevent, diagnose, and treat breast cancer not only impact direct health care costs, but may also influence indirect costs of productivity loss.