The research is intended to show the feasibility of developing a commercial ultrasound mammography system (non-ionizing modality) with a detection ability similar to x-ray mammography systems (lesions 5mm or less) and based on combined tissue and blood flow imaging. The blood flow imaging is significant, since malignant tumors exhibit dramatically increased vascularity and blood flow when measured with ultrasound Doppler. The instrument is intended for both screening and diagnosis. To overcome the limitations of conventional ultrasound mammography, the proposed work will evaluate several new imaging concepts: The received pulse-echo ultrasound RF data of a full image will be digitized which will give the greatly increased flexibility of software processing. The digital signal processing will produce both a tissue structure image and a blood flow image of the scanning plane. The negative pressure sensitivity of tumor blood flow will be investigated as a possible method of differentiating between benign and malignant lesions by use of special scanning tank. Using this scanning tank design will also permit the scanning to be performed with the woman in a sitting or standing position. For evaluation of the mammography system, ultrasound scanning of normal volunteers and women with diagnosed breast cancer is planned.