Between 10.01.1997 and 09.30.1999 authors performed operations on 78 patients who had nonpalpable breast tumors. If mammography was considered abnormal during breast screening program patients were recalled. Besides clinical investigation complimentary mammograms were performed. After sonogram, and if needed, aspiration biopsy cytology (ABC) if necessary core biopsy (CB) was the next investigation. 79 operations were performed on 78 patients (one was patient had synchronous breast tumor). The mean age of the patients was 56.3 years. If the radiological investigations (R4-R5) and/or the ABC (C4-C5) or CB suggested malignancy operation was performed. Mammography suggested malignancy in 60.75% of the patients, it was suggested by ABC in 30.18%, and by CB in 55.5%. The nonpalpable tumor, suspected to be malignant was marked with a wire loop and was excised under anesthesia along with the affected breast sector. The excision and tissue-border around the tumor was checked by specimen mammography performed during the narcosis. No cryohistology was performed. After the specimen mammography, the wound was closed. The final histology of the operations showed malignancy in 40.5%. In their retrospective study the authors evaluated the complete sensitivity and the positive predictive value (PPV) of the preoperative investigations regarding the final histology. They analyse the value of preoperative mammogram, the ABC and CB in malignant and in benign cases. Early diagnosis and surgical treatment is expected to improve significantly the survival of patients with breast cancer. Reduction in the number of unnecessary operations can be expected from increasing the accuracy of radiological and cytological investigations and the adequate usage of core biopsy.