The aim of this study is to determinate incidence and risk factors for loco regional failure (LRR) (breast, supraclavicular, axillary and internal mammary nodes) and indications for nodal irradiation. From January 1980 to December 2001, 4,185 patients with T1-T2 breast cancer were treated with conservative surgery and whole breast radiotherapy without nodal irradiation at the University of Florence. The median age was 55 years (range 19-86). All patients were followed for a median of eight years (range 3 months to 20 years). Multivariate analysis showed as independent prognostic factors for isolated nodal relapse (NR) the presence of more than three positive lymph nodes (PAN) (p = 0.001), angiolymphatic invasion (p = 0.002) and pT2 (p = 0.02). However, only 4.8% of patients with more than three PAN developed NR as the only site of recurrence. Having one to three PAN was not associated with an increased risk of NR. We believe that it is not necessary to prescribe nodal irradiation to patients with negative or one to three PAN. Regarding patients with more than three PAN, the number of isolated NR is also small to routinely justify a node irradiation.