The authors describe the retrospective analysis of treatment by 5-fluorouracil and interferon-a aof 34 patients with advanced colorectal cancer. An average of 4.6 treatment cycles (3 12) was applied. Complete remission was not observed; partial remission was observed in 8 patients; in 13 patients no change occurred and progression was detected in 14 cases. Remission rate was 22.8%, mean response time was 5.2 (3 12) months, mean progress-free survival 5.6 (0 22) months. Mean survival from the start of treatment was 11.9 (1 42) months and from the establishment of the diagnosis 26.1 (3 60) months. Severe life-threatening side-effects did not occur; other side-effects such as fever, nausea, diarrhea, leucopenia, and anemia responded to drugs. Treatment by 5-FU and interferon, in accordance with other authors findings, improved survival and well-being of patients but no breakthrough has been achieved.