Abstract: Objective : To explore the clinical value of diffuse optical imaging (DOI) with ultrasound localization (UL)in distinguishing benign from malignant breast tumors. Methods : We randomly selected 74 patients withbreast lesions seen in the ultrasound department of Tumor Hospital of Yulin from January to September of2007. These patients ranged in age from 22 to 64 years. The breast lesions were located by high frequencyultrasound initially and then examined by ODI with multiple wavelengths. The images reflecting blood oxy-gen-metabolism and density of angiogenesis in the tumors were obtained. The DOI with UL features of tu-mors were assessed according to the Breast Imaging Reporting and Data System (BI-RADS) defined by theAmerican College of Radiology (ACR). Class 1 to class 3 tumors are inclined to be benign and class 4 toclass 6 are inclined to be malignant. The DOI with UL and sonographic findings of breast lesions were com-pared with postoperative pathological findings and the accordance rate was assessed. Results : By the DOIwith UL, 30 lesions were recognized as BI-RADS 1 to 3 and 44 lesions as BI-RADS 4 to 5, indicating 30 cas-es of benign tumor and 44 cases of malignant tumor. Postoperative pathology showed that 34 lesions werebenign and 40 lesions were malignant. The sensitivity, specificity and accuracy of the diagnosis of the DOIwith UL were 95% (38/40), 82.4% (28/34), and 89.2% (66/74), respectively. Conclusion : DOI with UL can effec-tively distinguish benign breast lesions from malignant ones. This procedure obtains the 2D sonographic im-ages of breast lesions and provides further functional information. DOI with UL is a new method for the diagno-sis of early stage breast cancer that can potentially decrease the misdiagnosis rate of breast lesions.