Objective: We took intravascular threadlike structures from rat aortas to investigate their histological characteristics consistent with the intravascular Bonghan duct. Methods: Gomori s silver impregnation method, in addition to routine hematoxylin and eosin staining, was applied to demonstrate the characteristic feature of the intravascular threadlike structures. Results: These two staining methods clearly showed that the intravascular threadlike structures had unique features of argyrophilic reticular fibers and heavily stained oval or rod-shaped nuclei in them. Conclusion: The results are strong evidences for identifying threadlike structure as the intravascular Bonghan duct.