The recommended regimen for S-1 internal use is 4 weeks of daily medication and 2 weeks of drug holiday. However, we experience many cases where changing the regimen is ineffective because of adverse events. This time, we report a favorable case of alternate-day treatment with S-1 in an elderly patient with multiple lung metastases of colon cancer. An 84-year-old woman, performance status 2, was diagnosed as having colon cancer and multiple lung metastases. After operation of the colon, she received chemotherapy with the S-1 alternate-day treatment. The lung metastases decreased remarkably, and she was able to continue the treatment without significant adverse events. She has been receiving the treatment without progression for more than 18 months now. The alternate-day treatment with S-1 is reported as a cure with anticancer efficacy and few adverse events. This treatment seems to be a useful chemotherapy for elderly patients with colon cancer.