Any decision to biopsy a breast on the basis of findings discovered in a screening program must carefully consider the expertise of the clinical examination, the technical quality of the mammograms, and the skill and experience of the radiologist reading them. A positive clinical examination with or without mammographic confirmation is indication for biopsy. However, the surgeon must sometimes be governed solely by the report of the radiologist. On the basis of competent mammographic interpretation, patients without clinical evidence of disease face at least a 25% chance of having cancer. The area of concern must be carefully localized preoperatively and the specimen radiographed, particularly if it contains calcifications. This requires a clear understanding of the problem and complete cooperation between the surgeon, the radiologist, and the pathologist.