Obtivea: About seventy-five percent of the individuals with colon cancer will have a primary surgical resection with the hope of complete tumor eradication. Despite the high resectability rate and a general improvement in therapy, nearly half of all patients with colon cancer still die of metastatic tumor. Over the past three decades, many clinical studies have failed to demonstrate benefits from adjuvant therapy. Recently, new data from several studies have demonstrated delays in tumor recurrence and increases in survival for specific groups of patients. The objective of this study was to evaluate the effective- ness of 5-fluorouracil(5-FU) and low-dose leucovorin in reducing the recurrence rate and improving the survival of the patients with surgically resected colon cancer in stage II and III. Methods: One hundred and fifty six with surgically resected colon cancer in stage II and 1II from Nov 1989 to Dec 1993 were included in this study and were divided into two groups. First group(LF arm) included eighty five Patients who received combination chemotherapy of '5-FU and low-dose 1eucovorin' following resection of colon cancer, and second group(control arm) included seventy one patients who received only oral UFT or no adjuvant treatment. '5-FU and low-dose leucovorin' chemotherapy consisted of leucovorin 20 mg/m(2), intravenously, plus 5-FU 400 mg/m(2), intravenously, on days 1-5 every 4 weeks for 6 cycles. Results: I) There were significantly more recurrences and distant failure in control arm than LF arm. 2) The estimated 4-year disease-free survival was 82.5% in LF arm and 59.8% in control arm(p = 0.007). 3) The estimated 4-year overall survival was 94.3% in LF arm and 63.9% in control arm (p = 0.001). 4) The survival differences between LF arm and control arm were significant in stage II and III respectively. 5) Number of metastatic lymph nodes, histologic differentiation, and whether or not pa- tients received 5-FU/leucovorin chemotherapy, were each found to have prognostic significance. Concluslon: This study strongly suggests that 5-FU and low-dose leucovorin adjuvant chemotherapy is effective in patients with surgically resected stage II and III colon cancer.