Background: Breast cancer is considered the most common malignancy in females and the second most common leading cause of cancer death after lung cancer. Color, power and pulsating Doppler ultrasonography are more sensitive in the evaluation of solid breast mass depending on tumor new blood vessels growth that plays an important role in the growth of the malignant lesions. Aim of Work:To study the vascular structure of solid breast mass and to detect the importance of reversed diastolic flow in detection of malignancy.Material and Methods: This study included 114 solid breast mass in 100 female patients. Color Doppler ultrasound was done for all patients. We studied the blood vessels of the mass and we analyzed the wave pattern and detected the value of reversed diastolic flow in detecting malignancy. Results:The vessels in malignant breast mass are of irregular caliber with central penetration while regular peripheral parallel vessels are suggestive of benignity also we found that reversed diastolic flow is significant sign of malignancy. Conclusion:Color Doppler ultrasound is helpful to detect the vascular pattern of solid breast mass. Hypervascular mass with reversed diastole is suggestive of malignancy especially if the invading vessel is central and of irregular shape while presence of peripheral parallel vessels is suggestive of benignity however color Doppler indices such as high RI alone is not good indicator of malignancy.