S-(-)-N-[(1-ethyl-2-pyrrolidinyl)methyl]-5-iodo-2,3-dimethoxybenzamide (proposed generic name, epidepride) is a very potent dopamine D2 antagonist.It was synthesized by five steps from 3-methoxysalicylic acid.[131I]epidepride was obtained in 97.3% radiochem. yields from the corresponding 5-(tributyltin) derivative using hydrogen peroxide as the oxidant.The aryltin precursor was prepared from non-labeled epidepride by palladium-catalyzed stannylation using bis(tri-n-butyltin) in triethylamine.[131I]epidepride was stable under 4°, and partition coefficient was 72.3 at pH 7.40.The biodistribution study in rats exhibited high localization in the striatum of the brain with the striatum/cerebellum ratio reaching 237/1 at 320 min postinjection.All these results suggest that [131I]epidepride may be used widely as a useful dopamine D2 receptor imaging agent for SPECT.