Aim– Aim of the present study was to evaluate evidence of the histopathological changes occurring in the gingival epithelium and connective tissue in patients with chronic generalized periodontitis with and without diabetes. Material and methods– A total of 30 patients diagnosed with chronic generalized periodontitis (CGP) were divided into group I with controlled diabetes mellitus and group II without diabetes mellitus. Gingival tissues were obtained from patients undergoing periodontal flap surgery or after tooth extractions. The gingival tissue samples were fixed in 10% formalin, then processed by the usual technique of paraffin inclusion followed by staining with hematoxylin–eosin and masson’s trichromic stain. The histopathologic study was done to focus on the analysis of changes in the collagen fibres in two groups. Results– Biopsies from gingival mucosa of controls showed a squamous epithelium of normal histological aspect, with a thin layer of keratin, with rare and small sites of parakeratosis. Degradation of connective tissue was present in diabetic subjects, due to a rich inflammatory infiltrate, destruction of reticular fibers and accumulation of dense collagen fibers (fibrosis). Conclusion– Thus, the biopsies obtained from our study group shows that diabetes mellitus induces obvious histological changes, in both epithelium and gingival connective tissue.