Purpose: This is a Phase I/II study of preoperative concurrent radiation and chemotherapy in tethered and fixed rectal carcinoma. This study examined the curative resectability, the acute toxicities during chemo-radiation and the surgical complications. Methods and Materials: Between 1986 and 1990, 46 patients were treated with preoperative pelvic radiation (4000 cGy in 20 fractions in 4 weeks), 5-Fluorouracil infusion (20 mg/m2, days 1-4 and 15-18) and Mitomycin C (8 mg/m2, day 1). This was followed by surgery 6 to 8 weeks later. 30 patients had tethered tumors and 16 patients had fixed tumors. Results: After preoperative chemo-radiation, 41 patients (89%) underwent curative resection. Two patients (4%) had no residual tumor found (T0N0M0). Seven patients (1 5%) had nodal metastases. Two patients developed grade 3 neutropenia (WBC = 1-2 X 10(9)/L) during chemo-radiation. Five patients had delay in perineal wound healing. One patient had an anastomotic leak. Four patients developed stomal stenosis which required surgical revision. The 2-year actuarial survival was 73%. The 2-year local relapse rate was 16%. Patients with fixed carcinoma had a higher incidence of local failure (38% vs. 10%) and the difference was statistically significant (p = 0.0036). The 2-year distant failure rate was 41%, and the rates were similar for both tethered and fixed carcinomas. Conclusion: Preoperative pelvic radiation, chemotherapy and surgery could achieve a curative resection rate of 89% in tethered and fixed rectal carcinomas. However, distant metastases remained the major cause of failure.