PURPOSE: We retrospectively evaluated the impact of percent positive axillary nodal involvement on the therapeutic outcomes in patients with non-metastatic breast cancer receiving postmastectomy radiotherapy and chemotherapy. MATERIALS AND METHODS: Between January 1994 and December 2002, the medical records of 939 eligible non metastatic breast carcinoma patients were analyzed. Chest wall radiotherapy was indicated in case of positive surgical margin, tumor size equal or more than 4 cm, skin-fascia invasion. Lymphatic irradiation was applied for more than three metastatic axillary lymph nodes, incomplete axillary dissection (<10 lymph nodes), extracapsular extension or perinodal fat tissue invasion. A total dose of 50 Gy was given to chest wall and lymph node regions with 2 Gy daily fractions. Statistical analyses were performed by Kaplan-Meier method, Log-rank test and Cox's regression analysis. RESULTS: The median follow-up for all patients alive was 62 months. The 5-year overall survival (OS) and disease-free survival (DFS) for entire cohort were 81%, and 65%, respectively. Univariate analysis for OS revealed significance for tumour size (< or =5 cm vs. >5 cm, p<0.001), metastatic nodal involvement (0 vs. 1-3 vs. >4 LN, p<0.001), percent positive nodal involvement ([metastatic nodes/total nodes removed] x 100; 0 vs. < or =25% vs. 26-50% vs. >50%, p<0.001), surgical margin status (negative vs. positive, p=0.05), and hormonal treatment (present vs. absent, p=0.03). DFS had similarly significance for age (< or =40 years vs. >40 years, p=0.006), tumour size (0.02), metastatic nodal involvement (p<0.001), percent positive nodal involvement (p<0.001), and perinodal invasion (present vs. absent, p=0.01). Multivariate analysis revealed significance for tumour size, percent positive nodal involvement, hormonal treatment, and surgical margin status for OS. Age and percent positive nodal involvement were found to be significant for DFS. CONCLUSION: Percent positive nodal involvement was found to be a significant prognostic factor for survival in all end-points.