Objective To evaluate the clinical usefulness of 99m Tc MIBI imaging for the diagnosis of breast malignancy.Methods 195 patients with a total of 204 breast lesions were divided into three groups to undergo 99m Tc MIBI imaging and the results were compared with pathology.20 cases with normal breast served as control.Abnormal density showed by 99m Tc MIBI imaging in the breast(10% higher than surrounding structure) was regarded as positive.Results Of 100 breast cancer lesions,positive feature appeared in 92.Twelve out of 70 benign breast lesions showed positive imaging.Six out of 34 breast occult lesions were with positive imaging, among them 3 were finally found with carcinoma.No positive imaging was found in the control group.The diagnostic accuracy,sensitivity,specificity,positive predictive value,negative predictive value of 99m Tc MIBI was 92 0%,91 8%,92%,86%, and 92%,respectively.Conclusions[WT5”BZ] 99m Tc MIBI imaging has high sensitivity and accuracy in the diagnosis of breast cancer and in the differentiation between benign and malignant breast lesions.