Knowledge about the pharmacogenetics of metabolism of psychotropic drugs is based mainly on the study of the polymorphic enzymes CYP2D6 and CYP2C19. This chapter summarizes the knowledge on the pharmacology, metabolism, pharmacokinetics, and pharmacogenetics of antidepressants, antipsychotics, and methadone. Numerous psychotropic drugs are chiral and are introduced as racemates. Chiral drugs have one or several asymmetric centers: at least one carbon (or sulfur) atom of their molecule has four different atoms or groups attached to it. Most psychotropic drugs have active metabolites, and many achiral drugs give rise to chiral metabolites, the formation of which may be stereoselective and depend on the genotype of the patients. Chiral psychotropic drugs represent a useful tool for the study of neuropharmacological mechanisms and of the function of metabolizing enzymes. Many widely used drugs are introduced as racemic compounds, the enantiomers of which clearly differ in their pharmacology, metabolism, and pharmacogenetics.