Three cases of rhinoscleroma in the granulomatous stage were examined under the electron microscope. The rough endoplasmic reticulum of plasma cells in scleroma displayed cisternal dilatations forming Russell bodies and cytoplasmic vacuolations containing viable and degenerated bacilli forming Mikulicz cells. Thus, they play a double role, producing antibodies and providing protection for the intracellular bacilli. New ultrastructural findings of Klebsiella rhinoscleromatis bacilli were described.