OBJECTIVES The purpose of this study was to determine the frequency of occurrence of secondary tumors affecting other organs in case of patients suffering from tumor located in any fields of the breast. METHODS Data were collected from the financing database of the National Health Insurance Fund Administration (OEP). The subject of the observation aimed female patients treated in hospitals with primary breast tumor (BNO: C5000-C5090, D0570, D0590) between the period of January 1, 2002 and December 31, 2002. Accordingly we examined the frequency of occurrence of secondary tumors evolving after occurrence of the primary tumor in the following 5 years (2003-2007). RESULTS In 2002, a total of 10,378 patients (21,418 cases) were treated with malignant breast tumor. 2,870 primary breast tumor patients attended in hospitals with tumor disorders in any organs between 2003 and 2007. The first five malignant diseases appeared the most often in the examined period were: malignant tumors in the bones and bone marrow in 298 patients, malignant tumor in the lung in 212 patients, malignant tumor in the lymph gland in 186 cases, malignant tumor of the liver in 182 cases and malignant brain and dural tumor in 151 cases. The frequency of occurrence of these tumors projected on 10,000 primary breast tumors is the following: malignant tumors in the bones and bone marrow in 395 patients, malignant tumor in the lung in 281 patients, malignant tumor in the lymph gland in 246 cases, malignant tumor of the liver in 241 cases and malignant brain and dural tumor in 200 cases. CONCLUSIONS In the following 5 years of the primary breast tumor diseases other malignant tumors affecting other organs were evolved in 21.32% of the patients. In 26.67% of the patients no secondary tumors were evolved, but the primary tumor needed further treatment.