We have shaped a practical and rational treatment algorithm for major depression. This algorithm is based on evidence obtained by collecting documents from overseas and within Japan, considering the actual state of drug selection in Japan. Because of the characteristics of the drug treatment algorithm, there are several items that are important but could not be discussed, such as psychotherapy, light therapy, and so-forth. Both mild and moderate depression are outlined on the same algorithm because these two cannot be distinguished from the perspectives of pharmacotherapy available in our country.