The aim of the authors was to inform the professionals about the principles and methods of elaboration of one of the European Monitoring Centre for Drugs and Drug Addiction key indicators – the indicator of Problematic Drug Use on its concrete example of the local estimates for Bratislava. The authors expected that there will be remarkable difference among the results of different estimations derived from several surveys with the usage of different procedure s in the same city. Data collection was realized in the low threshold programs for drug users in Bratislava in the year 2005. The most reliable seems to be the estimates of lower and upper limits between 1.9 – 24.9 / 1000 inhabitants, that would be from 900 to 12 300 of problematic drug users, which was derived from the triangulation of all the results. It is also preferable with the respect to minimize the risk of politically simplified interpretations. The single estimation preferred by the authors would be one where the data were gathered from the contact centre and calculated with the number of all inhabitants living in the city as they were reported by different Bratislava districts. It was 7.4 – 24.9 / 1000 (from 3 600 to 12 300) persons with the central value of 5 600. The results indicate, that the character of the research data does not enable us to form an exact picture of the reality on the basis of a single estimation. Therefore, it is more proper to evaluate and to interpret the results of PDU carefully and to come to the real situation gradually using the approximation of more estimates from different source s and with different methods. Presentation of a wider interval and its prioritization to central value increases the reliability of the estimation and its practical predictive value.

Key words: estimates of drug use – problematic drug use – drug monitoring