The success and cost of needle localization biopsy (NLB) performed with local anesthesia in an outpatient procedure room (81 biopsies, group 1) or under general anesthesia in an operating room (36 biopsies, group 2) were compared in a longitudinal study. Only 78% of operations in group 1 successfully removed the target breast lesion; definite failure occurred in 17%, and results were indeterminate in 5%. Among lesions sought by group 2 procedures, 92% of lesions were removed successfully, 5% were missed, and 3% were indeterminate. The incidence of carcinoma in breast specimens was 17% in group 1 and 22% in group 2. Wound infection occurred after 6% of group 1 biopsies. The total cost of NLB was $775 in group 1 and $1960 in group 2. The difference in cost represented by the use of general anesthesia was $1260. The added expense of NLB done in an operating room under general anesthesia can be justified by a high rate of success in removing the breast lesion, by patient comfort, and by technical ease.