Interest has grown in genetic testing to personalize treatment approaches in psychiatry, especially mood disorders and to a lesser extent anxiety. However, numerous studies of genetic variants of metabolizing enzymes, along with fewer studies of single nucleotide polymorphisms of drug transporter proteins, receptors, and other putative drug targets such as neurotransmitter reuptake pumps and receptors, have reported contradictory findings that have not translated into practical, costeffective treatment recommendations. In this article, we review basic principles of genetic testing and highlight selected elements of genetic testing in cancer. We then critically review the current status of genetic research in pharmacokinetics and pharmacodynamics, as well as the few clinical trials that have been performed. After discussing the limited clinical applications of current research, we make recommendations for developing more clinically useful studies of cost-effective approaches to genetic testing in the treatment of mood and anxiety disorders.