[en] Purpose: To examine the relationship between lymphovascular invasion (LVI) and regional nodal failure (RNF) in breast cancer patients with zero to three positive nodes treated with breast-conservation therapy (BCT). Methods and Materials: The records of 1,257 breast cancer patients with zero to three positive lymph nodes were reviewed. All patients were treated with BCT at Massachusetts General Hospital from 1980 to December 2003. Lymphovascular invasion was diagnosed by hematoxylin and eosin-stained sections and in some cases supported by immunohistochemical stains. Regional nodal failure was defined as recurrence in the ipsilateral supraclavicular, axillary, or internal mammary lymph nodes. Regional nodal failure was diagnosed by clinical and/or radiologic examination. Results: The median follow-up was 8 years (range, 0.1-21 years). Lymphovascular invasion was present in 211 patients (17%). In univariate analysis, patients with LVI had a higher rate of RNF (3.32% vs. 1.15%; p = 0.02). In multivariate analysis, only tumor size, grade, and local failure were significant predictors of RNF (p = 0.049, 0.013, and 0.0001, respectively), whereas LVI did not show a significant relationship with RNF (hazard ratio = 2.07; 95% CI, 0.8-5.5; p = 0.143). The presence of LVI in the T2/3 population did not increase the risk of RNF over that for those with no LVI (p = 0.15). In addition, patients with Grade 3 tumors and positive LVI did not have a higher risk of RNF than those without LVI (p = 0.96). Conclusion: These results suggest that LVI can not be used as a sole indicator for regional nodal irradiation in breast cancer patients with zero to three positive lymph nodes treated with BCT.