In order to give a sound basis to a surgeon for the decision that a cancer should or should not be removed, an attempt was made to produce a regression equation to estimate postoperative survival. The relation between postoperative survival and the intraoperative gross-finding of the cancer, the age and sex of the patients, operative curability, histological types of the cancer and the need for combined resections of the adjacent organs were analyzed by the method of multivariate analysis (Quantification Method) in 111 patients with advanced cancer of the stomach. A statistically significant regression equation was obtained, by which the survival months were predicted for a prospective patient. This equation appears to be useful for surgeons as one way of deciding on an appropriate method of operation. The difference between the actual and the predicted survival months was less than twelve months in seventy-six percent of the internal samples.