The introduction of positive drug lists (positive lists) is part of the regulating mechanisms which try to reduce the increasing expenditure on drugs. An essential part of these provisions is at present an analysis of the trend of drug consumption. The objective of the work was to introduce and evaluate the method DU 90% which in analyses of drug consumption uses a 90% ratio of preparations of their total consumption.The analysis was focused on prescriptions in medical clinics of the General Faculty Hospital Classification of drugs according to anatomical, therapeutic and chemical groups and the use of defined daily doses made it possible to calculate DU 90% and to prepare a consecutive list of drugs according to costs in different departments. The number of drugs with a defined daily dose was within the range of 280-316. In the interval DU 90% were 116-142 drugs. In all departments there was a practically identical ratio of drugs which were part of the positive list. The greatest expenditure were anti-infectious drugs for systemic use and drugs with an effect an blood and haematopoietic organs.The advantages of the method DU 90% is its easy application, low cost and possibility to identify controversial lields. This facilitates further qualitative and quantitative evaluation of the standard of pharmacotherapy.