Mammography is the diagnostic method with the greatest usefulness, both in screening and in diagnosing breast cancer. However, although mammography is a highly sensitive technique, it is frequently incapable of differentiating malignant lesions from a benign one, having this method a positive predictive value (PPV) that ranges between 10 percent 40 percent. This PPV causes a large number of breast biopsies to be performed on benign lesions (unnecessaries). Furthermore, in young studies, fibrocistic disease, dense breast or evaluation after biopsy, surgery or radiotherapy, the perfomance of mammography is much lower and the diagnosis of the cancer is occasionally impossible. Bearing all these limitations in mind, the importance of a complementary diagnostic procedure that allows the PPV of mammography to be enhanced and that completes the study of patients who are difficult to evaluate by way of mammography becomes clear. It has been suggest that 99mTc-MiBi Scintimammography, used as a complementary technique to mammography, is a useful test in the examination of patients with suspected breast cancer. The adoption of a joint mammography-scintimammography diagnostic protocol could considerably reduce the number of biopsies performed in patients with lesions of low or indeterminate mammographic suspicion of malignancy (BIRADS 3,-BIRADS 4). Larger series will be necessary to determine the definitive value of this protocol, wich has been drawn up to select those patients with suspected breast cancer in whom a biopsy of the lesion schould be performed