A microwave imaging system has been developed as a clinical diagnostic tool operating in the 3- to 8-GHz region using multistatic data collection. A total of 86 patients recruited from a symptomatic breast care clinic were scanned with a prototype design. The resultant three-dimensional images have been compared "blind" with available ultrasound and mammogram images to determine the detection rate. Images show the location of the strongest signal, and this corresponded in both older and younger women, with sensitivity of [Formula: see text], which was found to be maintained in dense breasts. The pathway from clinical prototype to clinical evaluation is outlined.