Abstract Objective: This paper introduces an alternative non-invasive and non-ionizing breast imaging tool called vibro-acoustography (VA). This method is based on low-frequency harmonic vibrations induced in the object by the radiation force of ultrasound. Contrast in Vibro-acoustography images represent several properties of the object, including the dynamic characteristics at the audio frequency and scattering and absorption properties at the ultrasound frequency. X-ray mammography and ultrasound are the main imaging modality used today for detection of breast lesions. X-ray mammography, however, is ionizing and its sensitivity is greatly reduced in dense breasts. Ultrasound images suffer from speckles or other or artifact that prevents the physician from delineating the mass lesion from the background tissue. Hence, VA may be used as a stand-alone imaging device or as a tool to provide supplementary information to other existing imaging modalities. Materials & Methods: Matching vibro-acoustography and mammography images of human breast are acquired using a combined mammography/vibro-acoustography machine. Images of various types of breast masses are investigated and their characteristics features are compared. Image features, such as lesion borders, interior texture, and speculation pattern, are studied. Results: Resulting images show soft tissue structures, breast lesions and microcalcifications within breast with high contrast, high resolution, and no speckles. The results have been verified using x-ray mammograms of the breast. Vibro-acoustography images demonstrate that calcified masses normally show sharp borders, benign non-calcified masses have smooth texture, and, in some cases, malignant masses are characterized with spiculation. Conclusion: The encouraging results which are based on the data collected from an ongoing study indicate that the above mentioned image features may be used for differentiation of breast masses and suggest that further development of vibro-acoustography technology may lead to a new clinical tool for various imaging applications. Work supported in part by Grant CA121579-01A1from NIH and Grant BCTR#0504550 from Susan G. Komen Breast Cancer Foundation. Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 103rd Annual Meeting of the American Association for Cancer Research; 2012 Mar 31-Apr 4; Chicago, IL. Philadelphia (PA): AACR; Cancer Res 2012;72(8 Suppl):Abstract nr 4047. doi:1538-7445.AM2012-4047