PURPOSE: We performed a multicenter randomized controlled trial to determine whether postoperative adjuvant chemotherapy improves outcome in patients with esophageal squamous cell carcinoma undergoing radical surgery. PATIENTS AND METHODS: Patients undergoing transthoracic esophagectomy with lymphadenectomy between July 1992 and January 1997 at 17 institutions were randomly assigned to receive surgery alone or surgery plus chemotherapy including two courses of cisplatin (80 mg/m2 of body-surface area x 1 day) and fluorouracil (800 mg/m2 x 5 days) within 2 months after surgery. Adaptive stratification factors were institution and lymph node status (pN0 versus pN1). The primary end point was disease-free survival. RESULTS: Of the 242 patients, 122 were assigned to surgery alone, and 120 to surgery plus chemotherapy. In the surgery plus chemotherapy group, 91 patients (75%) received both full courses of chemotherapy; grade 3 or 4 hematologic or nonhematologic toxicities were limited. The 5-year disease-free survival rate was 45% with surgery alone, and 55% with surgery plus chemotherapy (one-sided log-rank, P =.037). The 5-year overall survival rate was 52% and 61%, respectively (P =.13). Risk reduction by postoperative chemotherapy was remarkable in the subgroup with lymph node metastasis. CONCLUSION: Postoperative adjuvant chemotherapy with cisplatin and fluorouracil is better able to prevent relapse in patients with esophageal cancer than surgery alone.