Antitumor activity of 1-hexylcarbamoyl-5-fluorouracil against various tumors was examined. Therapeutic ratio (ILSmax/ILS30) in L-1210 system was 4.5 by oral administration, while those of 5-fluorouracil and 1-(2-tetrahydrofuryl)-5-fluorouracil were 1.9 and 1.0, respectively. Therapeutic ratio of the compound in C-1498 system was 11, while those of 5-fluorouracil and 1-(2-tetrahydrofuryl)-5-fluorouracil were 3.3 and 2.5, respectively. 1-Hexylcarbamoyl-5-fluurouracil was also active against solid and ascites tumors by oral administration. It was markedly active against Nakahara-Fukuoka sarcoma, adenocarcinoma=755, and ascites sarcoma-180, and moderately active against Ehrlich ascites carcinoma. This compound had a wider tumor spectrum than 5-fluorouracil and 1-(2-tetrahydrofuryl)-5-fluorouracil by oral administration.