Development of Aripiprazole as an oral treatment of schizophrenia required the synthesis of a suitably labeled drug product for use in human metabolism and pharmacokinetic studies. Due to the potential metabolic degradation of the molecule, a multi-labeled approach utilizing C-14 was adopted. The synthesis of [C-14]Aripiprazole was accomplished in separate syntheses from 2,3-dichloro[U-C-14]aniline and [3-C-14]-cinnamic acid, respectively. Labeled versions were combined on the basis of molar radioactivity giving a final product with a radiochemical purity of 99.9% and a specific activity of 15.5 mu Ci/mg. Copyright (c) 2005 John Wiley & Sons, Ltd.