We attempted postoperative adjuvant chemotherapy for stage II or III colorectal cancer. To investigate the efficacy of the adjuvant chemotherapy, we retrospectively reviewed all 293 colorectal cancer patients who underwent curative resection between 1990 and 1996 in Kurume University Hospital. The patients were divided into two groups according to whether or not they received postoperative adjuvant chemotherapy. Patients in Group 1 (n = 156) underwent resection followed by administration of oral fluorouracil. Some also received intravenous 5-FU or MMC after surgery. Patients in Group 2 (n = 95) underwent surgery alone. The disease-free survival rate in Group 1 was significantly higher than that in Group 2, but only for those with rectal cancer, with no significant difference for those with colon cancer. The results were also analyzed according to tumor stage, degree of lymphatic and venous invasion, and histological grading. Findings were similar between the two groups for those with stage II, stage IIIa, a low grade of lymphatic and venous invasion, and well-differentiated adenocarcinoma. Postoperative adjuvant chemotherapy in colorectal cancer might reduce the risk of recurrence, particularly in cases of rectal cancer. However, postoperative adjuvant chemotherapy was insufficient for those with highly advanced cancer or a biologically aggressive tumor.