Previous studies of estimated costs for cancer treatment have been limited to elderly patients or to specific health maintenance organizations. Data from the statewide population-based Connecticut Tumor Registry on a random sample of 407 breast cancer patients diagnosed in 1991 were linked with a statewide hospital-discharge database, to estimate charges (through September 1993) for inpatient and ambulatory surgery care. For the 377 cases (92.6% of 407) successfully linked, average charges attributed to breast cancer care declined with age, increased with extent of disease (stage at diagnosis), and increased with extent of surgery; these associations persisted in multivariate analyses. Total hospital-related charges for comorbid conditions (during 1991-93) were considerable by age 45 to 64 years. The merged database should be most useful in estimating charges for: cancers treated mainly by surgery (including ambulatory surgery at hospitals); comorbid conditions; and terminal care.