The effect of application and of intravenous injection of bradykinin on the rat mesenteric microcirculation was studied by direct microscopy methods in vivo. Electrophysiological experiments failed to reveal the reaction of the vascular smooth muscle cells to bradykinin. Under the same conditions the dynamics of vasomotions was studied by the image-splitter method. It appeared that the microvascular response to bradykinin application varied and primarily depended on whether the application was primary or repeated. It is suggested that the action of bradykinin on the mesenteric vessels was mediated through the other vasoactive agents.