The purpose of this study was to determine the accuracy of 11-gauge stereotactic vacuum-assisted breast biopsy (SVAB) for the diagnosis of breast cancer. Percutaneous biopsies of 426 suspicious breast lesions in 365 patients using 11-gauge SVAB were performed between September 1996 and June 1998. Of these biopsies 59 (13.8%) resulted in a diagnosis of breast carcinoma and 56 (95%) were surgically excised. These 56 lesions constitute the basis of this study. Pathology of SVAB and surgically excised tissue of the 56 carcinomas as well as imaging findings were correlated. At percutaneous biopsy 34 (61%) lesions demonstrated ductal carcinoma in situ (DCIS) and 22 (39%) invasive carcinomas. Surgical excision demonstrated the presence of an invasive cancer in three lesions percutaneously diagnosed as DCIS (9%; confidence interval 2-24%). No residual carcinoma was surgically demonstrated in seven (12.5%) lesions. Sensitivity of 11-gauge SVAB for the diagnosis of invasion in breast cancer was 88 per cent. Using SVAB the diagnosis of invasive carcinoma is reliable. However, a percutaneous finding of DCIS does not exclude the presence of invasion in 9 per cent of cases as confirmed by subsequent surgery. Using SVAB 12.5% of carcinomas are completely excised.