The periodontal effects of food consistency and of experimental occlusal stresses were clinically studied with healthy and arteriosclerotic rats. Experimental arteriosclerosis was induced with a hypercholesterolemic diet continued for 6 -- 12 months. By using food that was finely powdered and moistened, mechanical irritation of the periodontium was reduced to a minimum. The special occlusal and gingival irritants lasting six weeks were an occlusal overload with an overhigh amalgam filling, or an occlusal hypofunction caused by extracting the antagonist tooth. The arteriosclerotic animals with experimental occlusal stress had gingival changes adjacent to the loaded tooth distinctly more often than around the control tooth on the contralateral side of the mandible of the same animal (P less than 0.001). The changes seen were local redness and inflamation, and an excessive hyperplastic growth of the gingiva. The gingival changes on the stressed side in control animals were generally slight and the difference compared to the contralateral side was not statistically significant. The control animals showed recession of the gingiva more often than hyperplastic growth of same. In both groups of animals food impaction and deposit of calculus had increased around the teeth that were in occlusal hypofunction. The inflammatory changes were more frequent in the arteriosclerotic animals than in the controls. The cause of the deterioration in the ability to repair tissue damage in arteriosclerotic animals is discussed.