We have developed a clinical pathway to enable the safe continuous administration of S-1 (TS-1) in ambulatory care for patients with advanced gastric cancer. The S-1 clinical pathway includes a pathway for clinicians, a pathway for patients, and such assist tools as a medication diary, an explanatory document containing instructions relating to patient compliance, a table of associations between adverse reactions and prodromes, and general principles for dose reduction and withdrawal. These pathways and assist tools will improve the patient's perception of adverse reactions, thereby contributing to early discovery and rapid action against adverse events. The S-1 clinical pathway has been used with ten patients. S-1 administration has been continued in seven patients. In four of the seven patients, continued administration on the occurrence of adverse reactions was made possible by the use of appropriate measures such as drug withdrawal or dose reduction. It was confirmed that the S-1 clinical pathway was a useful tool for cancer chemotherapy in ambulatory care.