Specimens were taken from the gastric cancer and that of noncancerous stomach on sides of the lesser and the greater curvatures, and 6-phosphogluconate was added to the homogenate of the specimen. Then the pentose-phosphate (p. p.) was measured before and after incubation. 1) P. p. before incubation shows lower level in the cancer case compared with the noncancerous. In both cases, the side of the lesser curvature has less p. p. than that of the greater. 2) The same results are also observed after incubation. 3) The increase of p. p. by incubation is more marked in the cancer case than the noncancerous. In both cases, the in crease is more marked on the side of the lesser curvature than that of the greater. 4) From these results, it is considered that the production as well as the consumption of p. p. are more marked in the cancer tissue than the non-cancerous, and also so on the side of the lesser curvature than that of the greater.