Although treatments for unresectable colorectal cancer have made great progress with new anticancer agents, they are still unsatisfactory. Development of anti-cancer therapy and its management are important in order to improve the treatment outcome of colorectal cancer. In the evaluation of treatment effect, obtaining a baseline image at the start of treatment is very important, and CT scan is generally performed for this purpose. In daily clinical practice, response evaluation criteria in solid tumors(RECIST)is usually adapted for the assessment of treatment outcomes. In addition, we should make decisions about continued therapy on the basis of both objective and symptomatic findings. Patients receiving palliative chemotherapy should be monitored with a CT scan every 2 to 3 months. It is important to make a treatment strategy individually in consideration of adverse events, purposes of the treatment, and tumor progression.