One of the urgent problems of modern medicine is to understand and explain the structural rearrangement of organs and tissues in the course of diabetes. The article presents the results of a comprehensive morphological study of the structural organization of micro- and macrovasculators, as well as some organs under conditions of diabetes mellitus in the experiment.  The study material constituted 52 adult outbred white male rats, with the average weight of 150-180 g, 4,5-6,5 months old. The following research methods were applied: histological, electron microscopic, biochemical, experimental modeling of streptozotocin-induced diabetes mellitus, morphometric and statistical. It was found that diabetic microangiopathy develops after 2 weeks of experimental diabetes, while after 4 weeks of the experiment there were some structural changes in the aorta observed. Furthermore, after 6 and 8 weeks, some profound destructive changes in the mandible and testis were revealed.  The obtained results may be used as fundamental data for the development of new methods for diagnosis, prevention and treatment of pathology of the cardiovascular system, oral cavity and male reproductive system caused by diabetes.