An iodinated dopamine D3 receptor ligand, [125I]trans-7-OH-PIPAT-A-trans-7-hydroxy-2-(N-n-propyl-N-3'-iodo-2 '- propenyl)aminotetralin, was developed. This ligand demonstrated unique high affinity and selectivity toward the dopamine D3 receptor; Kd = 0.48 nM and Bmax = 240 fmol/mg of protein in rat striatal membrane homogenates.