The degradiation and resorption of collagen in malignant tumor are investigated widely. The native collagen has resistance of the action of common protease at physiologic body temperature and pH. of somatic fluid. In 1963, Gross and Lapiere discovered an animal collagenolytic enzyme which act at neutral pH. and physiologic body temperature, by tissue incubation method. By this method, we measured collagenolytic activity of human stomach cancer, histological observations was performed simultaniously to study of the relationship between collagenolytic activity and morphological types of the stomach cancer. The results are follows: 1) In the cancer tissue stomach of the collagenolytic activity were significantly more high than non-cancerous tissue of stomach. 2) In the cancer lesion, the collagenolytic activity elevated at the spreading front. 3) On the surroundings of cancer lesion, the collagenolytic activity were not so high as cancer tissue, but sleightly higher than normal stomach ones. 4) On histological pattern, the well differenciated adenocarcinoma showed relatively high collagenolytic activity in both of center and spreading front of cancer lesion. In the poorly differenciated adenocarcinoma, the activity were low in the center but gradually arised in the spreading front. 5) On the collagenolytic activity by spreading mode, no difference was not seen in center and spreading front in massive continuous type, but in the non-massive interspersed type and non-massive continuous type, there was great difference between the spreading front and center of the cancer lesion. 6) The type of Borrmann I showed calacteristic distribution of collagenase activity, which was high in cancer lesion, but was low at the surrounding region, on the other hand, in the type of Borrmann IV it was elevated all over the whole stomach.