Preoperative localized mammary biopsy has been used as a diagnostic tool since before 1983 in the Breast Clinic, Ullevål Hospital. The great majority of procedures have been performed in the outpatient clinic with use of local anesthesia. Since 1988 all activity has been registered prospectively in a database. We discuss the use of the procedure and the results obtained during the period 1983-95. In the later part of the observed period, the use of the procedure as a diagnostic tool has been less frequent, but it has been increasingly used as a tool to identify the pathologic process when performing breast-conserving surgery. Surveillance of the malign-benign ratio is an important parameter in the quality assurance of the procedure. The malign-benign ratio has been greater than 0.3 during the period of observation. Continuous registration of procedure-related parameters is necessary for documentation of the results.