Image-guided core needle breast biopsy (IGCNBB) is an incisional biopsy technique that has been associated with tumor cell displacement. Theoretically tumor cell displacement may affect local recurrence rates in patients treated with breast-conserving therapy (BCT). We performed a study to determine if the biopsy method impacted local control rates following BCT. Patients with nonpalpable breast cancer (invasive and intraductal) diagnosed at our institution and treated with BCT between July 1993 and July 1996 were selected to provide a follow-up period in which the majority of local recurrences should be detected. Patients were divided into two groups based on their method of diagnosis. Group I patients were diagnosed by IGCNBB and group II patients were diagnosed by wire localized excisional breast biopsy (WLEBB). Factors potentially affecting local recurrence rates were retrospectively reviewed. Two hundred eleven patients were treated with BCT, 132 were diagnosed by IGCNBB and 79 by WLEBB. The two patient groups were similar when compared for prognostic factors and treatment. All patients' BCT included histologically negative margins. There were 4 (3.0%) local recurrences in Group I at a median follow-up of 44.4 months and 2 (2.5%) local recurrences in group II at a median follow-up of 50.1 months. This difference was not significant. Breast cancer patients diagnosed by IGCNBB can be treated by BCT with acceptable local control rates. Additional surveillance of our institutional experience and others' is mandatory to validate IGCNBB as the preferred biopsy method for nonpalpable mammographic abnormalities.