After many years of negative trials of adjuvant chemotherapy in colon cancer, two studies in the years 1989 and 1990 of the NCCTG and the Intergroup Trial, respectively showed a significant reduction of relapse and improved survival in patients treated with 5-FU and levamisole in an adjuvant setting. The absolute and relative reductions in 5-year-relapse and death rates were approximately 35% and 17%, respectively. Intraportal perfusion of the liver in an adjuvant perioperative setting seems to be of similar benefit. Preliminary data of the adjuvant therapy with 5-FU and folinic acid also show that this combination seems to have at least the same efficacy as the current standard 5-FU/levamisole in the adjuvant therapy of colon cancer. At the current time, patients with colon cancer of Dukes stage C should be offered adjuvant chemotherapy with 5-FU/levamisole outside of clinical studies.