Objective: To discuss whether T_2 breast cancer patients with 1-3 positive axillary lymph nodes after radical mastectomy need radiotherapy, and to determine the corresponding target region. Methods: We retrospectively analyzed 103 breast cancer patients treated in our hospital between 1997 and 1998. All pa-tients underwent radical mastectomy. Of these patients, 44 did not receive irradiation, 59 received irradiation to the internal mammary chain and supraclavicular area. All patients had no intumescent axillary lymph nodes or distant metastasis before radical mastectomy. T-test was used to analyze quantitative data, and ANOVA was used to analyze numerical data. Kaplan-Meier method and Log rank test were employed to calculate and compare the survival rate. Results: The 10-year survival rate was 56.8% in the non-irradiation group and 72.9% in the irradiation group (X~2=2.805, P=0.094). The 10-year disease free survival rate was 50.0% in the non-irradiation group and 64.4% in the irradiation group (X~2=4.063, P=0.044). The 10-year local recurrence rate was 27.3% in the non-irradiation and 10.2% in the irradiation group (X~2=5.112, P=0.035). The 10-year met-astatic rate was 43.2% in the non-irradiation group and 22.0% in the irradiation group (X~2=5.263, P=0.031).The 10-year chest wall recurrence rate in all patients was 7.8%. No patients had recurrence in the internal mammary chain area. Irradiation in the internal mammary chain area was useless and could not increase sur-vival rate and disease free survival rate. Irradiation in the internal mammary chain area was not helpful for re-ducing local recurrence rate or distant metastatic rate. Conclusion: Radiation therapy can reduce local recur-rence rate and metastatic rate in T_2 breast cancer patients with one to three positive axillary lymph nodes, and can increase survival rate and disease free survival rate. Recurrence in the internal mammary chain area is rare. Therefore, it is not necessary to irradiate the internal mammary chain area. We suggest that T_2 breast cancer patients with 1-3 positive axillary lymph nodes after radical mastectomy should have irradiation to the chest wall and supraclavicular area.