The ACRIN 6666 trial has shown that the addition of ultrasound or MRI to mammography screening detects more breast cancers in women with dense breasts and at least one other breast cancer risk factor. This higher detection yield is accompanied by an increase in false-positive findings. Unfortunately, this study was not randomized into groups with and without the addition of ultrasound and MRI. It is therefore impossible to investigate if the improved detection rate also results in a smaller number of interval tumours which would be the best indication of the ultimate goal - a decrease in breast cancer mortality. Before any new and costly imaging is added to the breast cancer screening program, it is necessary to investigate if this will not merely increase the detection of indolent tumours. If additional imaging is implemented too hastily it will be hard to turn it back, and impossible to assess it in a randomized study.