The number of positive axillary lymph nodes involved by tumor is one of the main prognostic factors for women with locoregional breast cancer (BC) for whom adjuvant chemotherapy is being considered. The prognostic importance of the ratio (P/D) between positive lymph nodes (P) and total dissected lymph nodes (D), previously demonstrated in the high-dose chemotherapy (HDC) setting has not yet been tested, however, in the conventional adjuvant chemotherapy setting. The data of 168 patients who were from 2 institutions and who were treated with adjuvant chemotherapy for BC were retrospectively analyzed, and univariate and multivariate analysis were performed, including the other traditional prognostic factors and P/D ratio as possible predictors of disease free survival (DFS). Disease-free survival for quartile 4 of P/D ratio (ratio >0.30) was statistically different from that for the other quartiles (log-rank test p < 0.001). Mean DFS for this series was not reached as well as for quartiles 1, 2, and 3, while mean DFS for quartile 4 was 44.5 months. In univariate analysis, number of positive lymph nodes (r2 = 0.055; p = 0.023), P/D ratio (r2 = 0.213; p < 0.001), and stage (r2 = 0.105; p = 0.002) were predictive of relapse, while in multivariate analysis, only P/D ratio remained an independent predictor of relapse (r2 = 0.213; p < 0.001). It is concluded that P/D ratio could become a simple, inexpensive, and easily available prognostic factor for patients undergoing conventional chemotherapy for BC.