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Objective: The present study was designed to evaluate the effects of the aerobic physical training (APT) on the structural and functional organization of the peripheral nervous tissue of rats with experimental diabetes mellitus. Methods: Male wistar rats (n=40) were divided into 4 groups: sedentary control (CS), trained control (CT), sedentary diabetic (DS), trained diabetic (DT). Diabetes mellitus was induced on the animals aged 60 days (intraperitoneal streptozocin, 60mg/kg). The exercise protocol consisted of forced-swim 1 h/day, 5 days/week, during 6 weeks. Serum glycemia, weight, nerve conduction velocity (NCV) and the action potential amplitude of the caudal nerve were measured weekly.. The sciatic nerve was collected 24 hours after the end of the APT period and mounted in paraffin blocks that were were sectioned in semi-thin and ultra-thin slices. The histomorphometric count and analysis of the endoneural vessels and the nerve area of each animal were with held through the scanning technique of all the microscopical fields (200X) and 75 endoneural microvessels (3-5/animal, n=5/group) were randomly ultramicrophotographed in the microscopical fields (8.900X) for morphometric analysis. The area and vascular perimeter, the area and lumen perimeter, the area and endothelial perimeter, and the pericyte area were registered. Thenceforth, the basement membrane length, the vessel wall length were established, and the amount of endothelial cell and pericyte nuclei were counted. The statistical analysis was using the average value ± SD, the comparisons among groups (ANOVA), and multiple comparisons post hoc using Tukey (p<0.05), were made. Results: All the endoneural microvessel areas suffered interference from the APT (p=0.016). The basement membrane length and the vessel wall length in the diabetic animals were not different when compared to the animals in the control group. However, pericyte cell hyperplasia was significantly higher in the DT rats when compared to the DS (DT 1.2±0.5 vs DS 0.7±0.4; p=0.038). Conclusion: All the endoneural microvessel areas measured in the diabetic animals suffered interference from the APT, in the same way the cellular activity, increasing the number of pericytes that envolve the endoneural microvessels. [ABSTRACT FROM AUTHOR]