Twenty-six patients with advanced colorectal cancer were treated with a combination based on multimodal biochemical modulation of 5-fluorouracil by means of high dose folinic acid, low-dose alpha-2b interferon and dipyridamole. The overall response rate was 42% (95% confidence intervals = 23%. 61%) with four complete remissions (15%). The median duration of response was 9 months and the median survival for responders was 15 months (all patients = 12 months). Toxic side effects included oral mucositis (grade III-IV = 38%) and a generally mild flu-like syndrome. This regimen seems active and safe enough to be compared with the combination of fluorouracil and high-dose folinic acid.