Colorectal cancer is one of the most frequent cancers in the world, especially in occidental countries. The primary curative therapy is surgical resection of the tumour. Within the last 15 years, appropriately powered prospective randomized trials have demonstrated that adjuvant post-operative chemotherapy should be the standard treatment for stage III cancers (node-positive disease). 5-Fluorouracil(5FU)/levamisole was used in the early 1990s but has now been replaced by 5FU/leucovorin. The recommended duration of treatment is 6 months. Combining levamisole with 5FU/leucovorin does not improve efficacy. In patients with stage II colon cancer it is still unclear whether adjuvant chemotherapy is effective. In an attempt to define groups of stage II cases that may benefit from adjuvant chemotherapy, considerable efforts have been made to determine molecular genetic factors (tumour-ploidy and mutations or alterations in oncogenes and tumour-suppressor genes). Regional therapy (particularly portal vein infusion) is one of the other therapeutic strategies still considered to be investigational. Current clinical trials are evaluating the role of non-fluorinated pyrimidine agents in an adjuvant setting.