Abstract: Objective To study the dynamic distribution of benzoapyrene in the bra in tissue of rat by light micro scopic autoradiography.Methods One hundred SD rats were divided in to control group and test group.The experimental anmials were given a single intravenous injection of 317×10⁵Bq/kg of 14C-benzoa pyrene while the same dose of normal saline was given to the control group.The rats were sacrificed at 1,6,12,24,and 48 hours after the administration of radio labelled benzoa pyrene.Lightmicroscopic autoradiography was used to observe the dynamic distribution of benzoa py rene in brain tissue.Results After the administration,the number of silver granules increased a long with the tmie increasing,which reached the peak in 24 hr and decreased sharply in 48 hr(P < 0.01).Light microscopic autoradiography showed that14C benzoa pyrene centralized in hippo campusat 1hr,in cerebral cortex at 6 hr,and in corpus striatum at 24 hr after the treamtent.The silver granule distribution was more in neuron than that of in neurog liocyte(P < 0.05).Conclusion Benzoa pyrene distributes unevenly in every region of ratbrain and the nerve cell is probaly the target cell of benzoa pyrene.