Twelve rabbits underwent 20-min of complete cerebral ischemia. They were given PGI2 for 3 min before and during ischemia and for 15 min after ischemia. Control animals with complete cerebral ischemia over the same period of time were not given PGI2 medication. The animals treated with PGI2 were found to have recovered bioelectric activity of the cerebral cortex in half the time that it took the control group. A positive effect of PGI2 on some parameters of the peripheral blood system after ischemia was observed. Under the conditions of this experiment PGI2 did not effect the ultrastructural changes in motor cortex neuron nuclei. The changes were manifested in numerous vesicular structures and nuclear inclusions. The inclusions took the forms of clusters, rodlets, and lattices constructed of filaments and/or tubules. The number of vesicular structures and inclusions grew with the lapse in time after ischemia.