PURPOSE: To estimate cardiac doses from breast cancer radiotherapy in Sweden from the 1950s to the 1990s. These doses will contribute to deriving dose-response relationships for the risk of radiation-induced heart disease. MATERIALS AND METHODS: The Swedish nationwide cancer register was used to identify women irradiated for breast cancer in the Stockholm area. Virtual simulation, computed tomography planning, and manual planning were used to reconstruct radiotherapy regimens. Estimates of heart and coronary artery dose were derived for each woman. RESULTS: Cardiac doses were assessed in 358 women. Mean heart dose varied from