A total of 27 patients with advanced or recurrent colorectal carcinoma were treated in a non-randomized open phase II study with a combination of 5-fluorouracil (750 mg m(-1) daily for 5 days as a continuous intravenous (i.v.)infusion followed, from day 15, by i.v. bolus 750 mg m(-2) every 7 days) and recombinant interferon-beta [r-hIFN-beta-1a; 9 MIU (total dose) by subcutaneous injection from day 1 on every Monday, Wednesday and Friday throughout the treatment period]. Here, IFNB1 is linked to colorectal carcinoma.