The aim of this paper was to study the clinical, biochemical and histopathological correlation caused by scaling and root planning in diabetic patients with periodontal disease.The study was conducted on 80 patients, both males and females, (age 25-60 years). Fourty patients had type 1 and type 2 diabetes, while 40 were non-diabetic patients. According to the medical examination, the subjects including in the study were well-compensated. After studying the periodontal field, patients with real pockets measuring 5 mm or less were selected. LABORATORY CRITERIA: The subjects were considered to be diabetic when their basal glycemia was equal to or above 140 mg/dl, and the HbA1C equal to or above 8%. Patients whose glycemia was below 115 mg/dl, and their HbA1C below 8% were considered to be non-diabetic. Free and inserted biopsies of the gingiva were done after the administration of 2 g of amoxicilin. Scaling and planing of all the teeth was carried out and periodontal protection was placed. Supervised dental sessions were held weekly. Clinical and biochemical criteria for selection were used again at 40 days and at 120 days. Biopsies were done and analyzed microscopically.At 40 days and mainly at 120 days it was found that in 90% of the selected patients glycemia values had decreased. In 70% of the cases studied HbA1C values were stable and the clinical signs of the periodontal disease were reversed in 80% of the subjects. Histological analysis at time 0 revelead mononuclear infiltrate, congestion and proliferation of the middle layer of the vessels when compared with non-diabetic values with deposits of PAS + material. At 40 days and at 120 days there was also a decreased of infiltrate and of the deposits PAS + on the wall of the small vessels.Scaling and planning is proposed as an effective method to reverse glycemic values, HbA1C, gingival microangiopathies and clinical signs in diabetic patients with periodontal disease.