TDM of psychotropic drugs was introduced almost 40 years ago and it constitutes now a widely accepted tool for optimising pharmacotherapy in psychiatric patients. This was possible thanks to the development of sophisticated analytical procedures for drug assays and of a specific clinical pharmacological approach of drug treatments, and by the introduction of rating scales for the evaluation of the efficacy and adverse effects of drugs in patients. In parallel, knowledge increased dramatically with regard to the influence of genetic and environmental factors determining the fate of the drugs in the organism. It is particularly helpful to explain pharmacokinetic interactions between drugs and clinical consequences, and this led to the recommendation of the combination of TDM with pharmacogenetic tests in specific situations. On the other hand, despite the abundant literature, there was a lack of consensus about the optimal use of TDM in psychiatry. Therefore, an interdisciplinary group of authors in central Europe, members of the AGNP (Arbeitsgemeinschaft fuer Neuropsychopharmakologie und Pharmakopsychiatrie, Association for neuropsychopharmacology and pharmacopsychiatry), developed consensus guidelines for the optimal use of TDM (Baumann et al., 2004 a and b), which were then also translated in German and in French. Briefly, they comprise a review on the pharmacokinetics, the metabolism and pharmacogenetics of psychotropic drugs, but also on their analysis in blood. The core of these guidelines is constituted by a catalogue of indications for TDM, by general and drug-specific recommendations for the physicians and the laboratory and by tables which summarize optimal drug plasma concentration ranges. An analysis of the literature shows that these guidelines are still unique but also, that the recent introduction of new drugs and the progress realised in the field of TDM and related subjects suggests that an updating of these guidelines would be useful.