Raclopride is a selective dopamine D2/D3 receptor antagonist with Ki values of 1.8, 3.5, 2,400, and 18,000 nM for D2, D3, D4, and D1 receptors, respectively. It passes the blood brain barrier and can be used in in vivo binding and autoradiography studies of the dopamine system under normal and pathological conditions such as Huntington’s disease.