Pharmacokinetics of psychotherapeutic drugs has specific problems, related to the sensitivity of determination methods or interindividual differences in metabolism of these compounds. Furthermore, some metabolites have psychopharmacological activity. The significante to pharmacokinetics of variables, such as sex, age, race and daily habits has not been studied sufficiently upto now. This means that pharmacokinetics can answer only partially to questions regarding dose, dose interval and individual therapy control, and so just for some psychotherapeutic drugs. Further investigations are urgently needed, before prediction of the clinical effective dose of these compounds will become possible by pharmacokinetic parameters.