This histochemical study showed that experimentally arteriosclerotic rats, subjected to an occlusal stress of six weeks’duration, showed an inflammation-related increase of chloride-activated arginine aminopeptidase and acid phosphata-se activity in the basal cells of the gingival epithelium. The activity of chloride-activated arginine aminopeptidase and acid and alkaline phosphatase in the gingival connective tissue was slight and suggestive of chronic inflammation. Biochemical comparison of gingival specimens from the stressed and unstressed sides of the jaw in the experimental animals failed to reveal any difference in the rate of N-L-arginyl-2-naphthylamide hydrolysis induced by the Cl-ion in connection with occlusal disorder. On the other hand, the mean value of the enzyme activity was lower in the experimental animals than the controls (p<0.5). The difference was assumed to be associated with degenerative tissue changes. The hydrolysis of p-nitrophenyl phosphate at acidic and alkaline pH in the gingiva was higher in the experimental animals than in the controls, and in the alkaline pH range the difference between the mean values was statistically significant (p<0.01). This finding, which may be associated not only with gingival inflammation but also with other tissue changes, requires further investigation.