Elasticity (mechanical strain) imaging is under rapid development as a tool to improve the specificity of breast ultrasound imaging. Elasticity imaging exploits the fact that benign and malignant breast disease cause inherently different tissue stiffness. We performed a retrospective observer study to determine if elasticity imaging can improve radiologists risk assessment for breast masses over risk assessed with conventional B-mode imaging alone. The best examples of 50 malignant and 48 benign cases were chosen that also represent the distribution of disease from the full data set of 403 breast masses. Other studies precede ours, but our experimental design is unique and this is the first multi-institutional study with multiple expert readers blinded to the tissue pathology. Elasticity imaging was found to increase the ability to assess risk for all observers.