This work describes changes ill relative blood flow caused by discrete emboli reaching the brain of conscious rabbits. With [C-14]iodoantipyrine autoradiography, small ischemic foci were observed scattered throughout the brain. After correction for tracer diffusion from the surroundings, the ischemic regions located in the deeper parts of the brain were found to have a lower blood flow than the foci in the cortex, Further, the cortical foci were significantly smaller than those in the basal ganglia (the area where the average size of the foci was found to be largest). The results and conclusions of this work should aid in interpretation of future experiments with potential treatments. Microinfarctions may well need different treatments depending on their localization. (C) 1998 Academic Press.