Pharmacogenetics is a discipline that studies interindividual differences in DNA which cause a variable drug therapy response. The ultimate goal of pharmacogenetics is the establishment of treatment on the principles of so-called Personalized medicine, in which every person or patient is managed as an individual. The way in which it is achieved - is to determine its pharmacogenetic status by molecular diagnostic methods and thus provide the possibility of adjusting the treatment to each patient’s needs. The aim of this paper is to systematically present pharmacogenetic principles up-to-date information and treatment recommendations, to make them available to clinicians and other users, thus promoting the use of pharmacogenetics in clinical practice. Particular emphasis has been put on the clinical interpretation of the guidelines which are the basis of drug choice and dosage, with variable outcomes and side effects that depend on the pharmacogenetic testing result. In addition to a systematic overview of the relevant sources available and applicable today, as well as the pharmacogenetics and pharmacogenomic potential in drug development phases, a critical review of the pharmacogenetic principles has been made, with regard to the constraints that make them difficult to be introduced into clinical practice. Among these limitations are the price of molecular tests, their relative inaccessibility, and the complexity of the interpretation of results. This work is the basis for the construction of a Croatian language website - manual in the near future, which would provide easier access to information on pharmacogenetic treatment principles and specific tests availability to clinicians and other interested users. In conclusion, pharmacogenetics and pharmacogenomics provide great opportunities to improve the quality of health care for each patient. However, they make sense while being economically viable, i.e. determining a therapeutic profile does not exceed the financial resources that would be spent using conventional therapeutic procedures.