Phase II study of 5'-DFUR was conducted in 195 patients with malignant tumors by the Osaka Chemotherapy Cooperative Study Group. Five CR and 20 PR cases were obtained out 133 evaluable cases and the total response rate was 18.8% (15.8% in gastric, 38.1% in breast) One PR was observed for each of head & neck and esophageal cancer. It was noteworthy that four CR were observed in breast cancer. Adverse reaction was observed in 61 out of 151 cases (40.4%), and major side effects were digestive symptoms such as diarrhea (22.5%), nausea-vomiting (11.9%) and anorexia (10.6%). These results suggest that 5'-DFUR can be useful for the treatment of malignant tumors.