The current study was performed to determine whether the Mammotome, a new breast biopsy instrument, is better at harvesting breast tissue percutaneously than an automated Tru-Cut (ATC) device. A total of 345 stereotactic breast biopsies were performed with the Mammotome. The Mammotome specimens were clinically evaluated on a five-point specimen scale that reflected the quality and quantity of the specimens and the rapidity of collection. In selected cases, specimen weights from both techniques were measured. In addition, by examining the lesion site post-biopsy, biopsies were categorized as incisional or excisional. Specimens obtained with the Mammotome were two times heavier than when obtained with the Biopty gun (34.3 mg vs. 17.2 mg, P < or = 0.0002). When aggregate Mammotome specimen weights were regressed against number of specimens submitted, average weight per specimen was 31.9 mg (P < or = 0.0001). When compared with the ATC device on the specimen scale, the Mammotome specimens were rated "Average" in 2.1 percent, "Good" in 13 percent, and "Very Good" in 84.9 percent. Also, 51.9 percent of the biopsies with the Mammotome were judged to be incisional; 48.1 percent, excisional. Three minor complications were encountered. The Mammotome more quickly harvests more breast tissue compared with ATC technology.