With the aim of establishing a topical chemotherapy against stomach carcinoma, 5-fluorouracil (5-FU) emulsion (oil/water type) for injection has been developed. The drug distribution was analyzed by 5-FU bioassay and radiographic examination of soft parts, for which radiopaque Lipiodol was employed in an oil phase. In order to examine local toxicity, tissue retention, and transfer to lymph nodes of 5-FU emulsion, the drug was administered perorally to rats and injected intramurally through the gastric serosa into laparotomized dogs. Following this series of experiments, which gave satisfactory results, the time courses of drug concentration in the gastric wall and regional lymph nodes were studied as a pre-clinical trial, by applying endoscopic intramural injection of 5-FU emulsion or solution in dogs. The anti-metastatic and anti-neoplastic effects of 5-FU emulsion were investigated in an experimental model of lymph node metastasis in mice. The emulsion was more effective in subduing metastasis and tumor growth than the solution, and the effectiveness of the former was further augmented by the use of repeated injections rather than a single injection. This method of endoscopic injection of 5-FU emulsion should be of great value as a local therapeutic measure against stomach carcinoma itself as well as against metastatic lesions in the lymph nodes.