Stereotactic large-core needle biopsy is increasingly replacing needle-localized breast biopsy for the diagnosis of nonpalpable breast disease. In this prospective study, the impact of the introduction of this technique on diagnosis and surgical treatment of nonpalpable breast cancer was assessed in two hospitals in The Netherlands.A total of 84 patients with nonpalpable breast cancer, diagnosed by means of stereotactic large-core needle biopsy (needle biopsy group) were compared with 80 patients diagnosed with nonpalpable breast cancer before the introduction of large-core needle biopsy. These patients were diagnosed by means of needle-localized open breast biopsy (control group). Clinical outcome measures evaluated included: duration of diagnostic and therapeutic intervals and number of surgical procedures required for complete surgical treatment. Subgroup analysis was performed for the category of microcalcifications without tissue distortion.For the needle biopsy group, the median interval between initial referral to the surgeon and the availability of histological diagnosis was 9 days and the interval between initial referral and complete surgical treatment was 31 days. These intervals were significantly longer for the control group (19 days and 44 days respectively); 75% of patients in the needle biopsy group were treated in a single step surgical procedure compared to 16% of the patients in the control group (67 vs 25% respectively for the subgroup). The mean number of surgical procedures required to complete surgical treatment was 1.31 for needle biopsy group vs 1.91 for the open biopsy group (1.46 vs 1.84 for the subgroup).Introduction of stereotactic large-core needle biopsy leads to a reduction of the time to diagnosis and the time to complete surgical treatment of nonpalpable breast cancer. It also reduces the number of surgical procedures required for complete surgical treatment of nonpalpable breast cancer. The benefits of large-core needle biopsy may also be anticipated for patients with microcalcifications without tissue distortion.