One-third of colorectal cancer patients suffer from liver metastases on initial diagnosis. Overt liver metastases appear to be the first site of relapse for 40% to 50% of the patients with operable disease. The fact that tumor cells can be discovered in the mesenteric blood during surgery may indicate that circulating tumor cells give rise to metastases. Experimental investigations have shown that metastatic tumors reaching a diameter of 5 to 7 mm are predominantly perfused by the arterial route, which explains the unsuccessful attempts to treat established liver metastases through the portal vein. However, because metastases in the liver presumably arise via blood flow through the portal vein, adjuvant intraportal chemotherapy might permit ready access of the drug to small liver deposits in a way that systemic chemotherapy might not. The interest in portal adjuvant cytotoxic liver infusion in radically resected colorectal cancer patients is based on an early publication by Taylor, who in 1979 reported on a significant reduction of the incidence of liver metastases in a group of patients randomly assigned to perioperative adjuvant portal infusion with 5-fluorouracil. Based on these results, several groups initiated prospective randomized trials comparing intraportal infusion of various regimens to surgery alone. Results of most of these trials have been published during the last few years. All but one demonstrate improved overall survival and disease-free survival and a reduction of the incidence of liver recurrences in the adjuvant-treated patient group. Ongoing meta-analyses of the randomized trial data may confirm this tendency soon.