The impregnation method and micropreparation were used to study the morphological changes in vessels of the microcirculatory channel of serous membranes in systemic allergic vasculites. Inflammatory and sclerotic processes in arterioles, precapillaries, capillaries, postcapillaries, and venules were found to be accompanied by regeneration changes and complicated adaptative alteration of the intact structures of the terminal vascular bed. The paper also presents morphological data reflecting decompensation processes in local lymph and blood flow.