Two trials were carried out in order to compare, in two similar groups of patients, the efficacity of 5-fluorouracil (5FU) with or without BCG. The first trial comprised 159 patients with different forms of carcinoma. The differences in survival rate between the 77 patients treated with 5FU and the 82 patients who had received 5FU and BCG seem to be in favour of the combined treatment, but are not statistically significant. The second trial (20 cases treated with 5FU and 23 cases treated with 5FU and BCG) concerned patients with Dukes' Stage B and C colorectal cancer; the results of the combined treatment are clearly more favourable.