PURPOSE: To evaluate the pathologic effects of preoperative radiotherapy on the resectable distal rectal cancer, we analyzed the results of postoperative pathologic findings for the patients with preoperative radiotherapy and surgery. MATERIALS AND METHODS: From July 1995 to April 1996, we treated sixteen patients of resectable rectal cancer with preoperative radiation therapy and curative surgery. At diagnosis, Thomas Jefferson (TJ) system was used for the clinical stage of the patients. We treated the patients with conventional radiation therapy of 4500-5000cGy before surgery. The surgery was carried out 4 weeks after completion of radiation therapy. Modified Astler Coller (MAC) system was used for the postoperative pathologic stage. We analyzed the pathologic stages and findings according to preoperative clinical stage and compared with those of the control group in similar clinical stages. RESULTS: All patients were treated with sphincter preservation surgery after preoperative radiation therapy. Pathologic complete response (CR) was shown in 1 case (6.3%). We compared the results between preoperative radiation therapy group (Preop.RT group) and surgery only group (control group). In TJ stage II, among nine patients of Preop.RT group, 8 patients (88.9%) were in MAC stage B except 1 CR patient, but among 17 patients of control group, 11 patients (64.7%) were in MAC stage B and 6 patients (35.3%) in MAC stage C. In TJ stage III, among 7 patients of Preop.RT group, 4 patients (57.1%) were in MAC stage B and 3 patients (42.9%) in MAC stage C. Among 14 patients of control group, 4 patients (28.6%) were in MAC stage B and 10 patients (71.4%) in MAC stage C. Above results showed that postoperative pathologic stage was decreased in Preop.RT group with statistical significance (p=0.049). The postoperative pathologic findings (blood vessel invasion, lymphatic vessel invasion, perineural invasion) were decreased in the Preop.RT group compared with those of control group. But statistical significance was found only in lymphatic vessel invasion (p=0.019). CONCLUSION: The postoperative pathologic stages and adverse prognostic pathologic findings were decreased in preoperative radiation therapy group. The lymphatic vessel invasion and MAC stage C findings were abruptly decreased in preoperative radiation therapy group. The preoperative radiation therapy was found to be effective in resectable rectal cancer. The patients group in our study was very small and long term follow up was not done. Therefore, further study about this issues is needed .