OBJECTIVE To retrospectively determine the lesion miss rate and false-negative rate of needle-localized open breast biopsy (NLOBB) with stereotactic guidance in a large study population. METHODS The ethical review board approved the study; the need for informed consent was waived. A total of 1115 stereotactic NLOBBs performed in 1068 women aged 22-90 years (mean age, 54 years) were tracked to determine outcomes. In cases of malignancy, NLOBB was considered to be diagnostically successful. The mammographic outcomes in all patients with benign results at NLOBB were tracked for at least 2 years. Cases without such mammographic follow-up were cross-referenced with a tumor registry after at least 54 months. The lesion miss rate was based on all malignant lesions and all lesions with long-term mammographic follow-up. Results from all 1115 NLOBBs were used to report the false-negative rate. RESULTS Of 1115 NLOBBs, 472 (42%) had malignant results. Mammographic follow-up data were available for 535 (83%) of 643 NLOBBs with benign results. Mammographic follow-up revealed 11 lesions that were missed with NLOBB, of which five were malignant and six benign. Thus, the lesion miss rate with NLOBB was 1.1% (11/[472 + 535]). Among the 643 cases, in 108 of them without mammographic follow-up (17%), cross-referencing with a tumor registry did not reveal missed cases of breast carcinoma. The false-negative rate was therefore 1.0% (5/[472 + 5]). CONCLUSIONS On the basis of the results of long-term follow-up, the authors noted a lesion miss rate of 1.1% and a false-negative rate of 1.0%, which indicate that NLOBB with stereotactic guidance is an accurate method for diagnosing breast lesions.