Nonpalpable breast tumors are of great importance in order to achieve early diagnosis and improve the treatment results of breast cancer. Three hundred and sixty six patients with such pathology were investigated at the Institute of Oncology, Vilnius University. The core biopsy was performed for all patients. Benign breast tumors were diagnosed to 260 patients and conservative treatment was administered to patients with benign breast disease. One hundred and six patients with diagnosed or suspected nonpalpable breast carcinoma underwent surgery. In 64 patients (63.7%) invasive or non-invasive breast carcinoma (0 and 1(st) stage - 71.9%) was diagnosed. The diagnostic algorithm of nonpalpable breast tumor was described. The techniques of surgery for nonpalpable breast tumors and the results of treatment are discussed.