This investigation is part of an ongoing large scale study using volumetric breast ultrasound (VBUS) as a screening modality in mammographically dense breasts, offering a substantial benefit to MR imaging of the breast in terms of cost and efficiency. The addition of VBUS to mammography in women with greater than 50% breast density resulted in the detection of 12.3 per 1,000 breast cancers, compared to 4.6 per 1,000 by mammography alone with an overall attributable risk of breast cancer of 19.92 (95% confidence level, 16.75-23.61) in our screened population. These preliminary results may justify the cost benefit of implementing the judicious use of VBUS as an alternative to MR imaging of the breast in conjunction with mammography in the dense breast screening population.