Many problems such as non-response, pharmacokinetic interactions with clinical consequences and adverse effects (pharmacovigilance) may be observed in patients submitted to psychopharmacotherapy. These risks are increased in patients belonging to the category of "special populations": elderly patients, children and adolescents, patients with a genetic particularity of metabolism or suffering from somatic or psychic comorbidities. Pharmacokinetic and pharmacogenetic tests are useful to solve problems in psychopharmacotherapy and thus improve efficacy and safety. Therapeutic drug monitoring (TDM) is particularly recommended in situations presented above and in patients who are non-compliant. In addition, the use of generics has been shown to represent a source of unexpected treatment outcomes, and TDM may help to explain pharmacokinetic particularities after switching from an original to a generic preparation (or vice versa). Finally, the increasing knowledge of the metabolism of psychotropic drugs allows taking account of the pharmacogenetic status (e.g. cytochrome P-450, P-glycoprotein) of the patients not only in adapting their medication, but also for interpreting pharmacokinetic interactions with clinical consequences. In this respect, pharmacokinetic and pharmacogenetic tests have now also to be considered as a tool in pharmacovigilance programs. Psychiatrists who already have experience in this field will have their knowledge updated: recent progress will be illustrated by clinical situations, which will be discussed in an interactive way. A consensus paper with recommendations on the optimal use of pharmacokinetic and pharmacogenetic tests will be summarized and submitted for discussion.