This retrospective 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 5 years following diagnosis. 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 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. Total average costs of breast cancer amounted to 107,456 <euro> 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 5 years following diagnosis. Patients with advanced breast cancer stadia had higher health care costs. Cost estimates provided by this analysis can be used to determine priorities for, and inform, future research on breast cancer. In particular, attention needs to be focussed on decreasing productivity loss from breast cancer.