One hundred and eighty-nine dentulous patients with diabetes mellitus and sixty-four patients believed free of diabetes were examined for periodontal disease. Certain variables were measured and related by computer analysis to the degree of observed gingival pathology. The findings indicate that the prevalence and severity of periodontal disease are increased in the diabetic patient. In addition, the periodontal index was related in positive fashion to age, duration of known diabetes, diabetic complications, and variation of blood sugar levels.