The researchers suggest that diabetes increases the degradation of the newly synthesized collagen from the conjunctive tissue. The altered metabolism of the collagen may predispose the diabetic patients not only to periodontal disease, but also to some other anomalies such as defective healing. The purpose of the study was to go through a histological analysis of the collagen fibers from the chorion in patients with diabetes mellitus and periodontal disease. Materials and methods:In our study we examined a total of 68 patients diagnosed with diabetes mellitus type 1 and 2. In these patients we achieved simple gingivectomy or tooth extraction in order to obtain gingival tissue fragments. The preparations included at paraffin and then stained with Hematoxylin-Eosin and trichromic after Goldner-Szeckeli method. Results:In the patients with diabetes mellitus with an evolution of less than 10 years the collagen fibers appeared as dissociated by the inflammatory cells that were inserted among them. It was also noted the fragmentation of collagen fibers and sometimes even their lysis with subepithelial connective tissue disorganization. In patients with diabetes for over 10 years there has been noticed a plentiful collagen sclerosis, zones of collagen hyalinization with an increased number of fibrocytes. Conclusion:The extracellular matrix is altered in the investigated patients with destructive lesions of collagen or collagen sclerosis.