The author reviewed the effect of psychological factors on the development and course of cancer. Cancer is a bilogical disease, but it also has a large number of psychological aspects. There have been no reports that specific personality types had tendency to cause cancer. In some studies, however, type A personality was reported to have relevance to a higher incidence of cancer and a better prognosis. And in other studies, type C personality was reported to have relevance to a higher incidence of cancer. It was reported that people who had strong tendency to control their anger and regarded the rationality and antiemotionality in their behavior as important things were susceptable to cancer. In the course of cancer, the patients who had more positive and aggressive attitude and 'fighting spirit' to their disease tended to have a better prognosis than those who accepted their disease as fate. Some studies showed that feeling of helplessness and loss of control had a negative offset on cancer. It was reported that, in the early stage of cancer, the psychological factors had great influence on the prognosis, but in the middle and late stage, the influence decreased. For the future studies, cancer should not be regarded as a single disease and a single condition. The kinds and stages of cancer should be difined for studies. The scales for psychological evaluation for cancer patients should be sensitive and selected carefully, considering the complexity of the cancer patients mind. The need for prospective studies is emphasized. Finally, as the cured cancer patients have great difficulties in returning to their work and daily life, rehabilitation of cancer patients is also emphasized.