Oxyradical-dependent chemiluminescence from granulocytes sticking to venular endothelium was successfully visualized in rat mesenteric microvascular beds treated with platelet-activating factor (PAF). Intravital photonic image intensifier microscopy revealed that topical application of PAF-acether (100 nM) caused remarkable granulocyte adherence on endothelial walls and the subsequent activation of a luminol-dependent photonic burst. Chemilumigenic sites clearly corresponded to the spatial distribution of sticking cells in post-capillary venules. The present findings thus serve as the first demonstration of an intravital oxidative burst of granulocytes on venular endothelium in PAF-induced microcirculatory disturbances.