An evaluation of frequency and intensity of the megakaryocytic emperipolesis in the rat bone marrow after unilateral carotid artery occlusion was performed. The results were compared with those obtained in the group undergoing a blood loss and the group not subjected to surgical procedures. A significant increase in the frequency of emperipolesis was found in the bled rats following a carotid artery cannulation, but also in animals exposed to the carotid artery occlusion only. In most cases the cytoplasm of megakaryocytes contained granulocytes and erythroblasts. The observed emperipolesis phenomenon is likely to be a result of brain hypoxia and a secondary neurogenic stimulation of the bone marrow activity.