OBJECTIVES: The aim of this study was to collect comparable and reliable data on the antibiotic consumption in Slovakia during the period 1998 – 2002. The special interest was paid to the trend of the macrolides usage and the resistance of Str.pyogenes. Antibiotic treatment and the pharmacoeconomic analysis of tonsillitis treatment was evaluated. METHODS: For the period 1998-2002, data for the ambulatory and hospital care were collected following the ATC/DDD classification. The results were expressed in the numbers of the packages, finance units (SKK) and Defined Daily Doses per 1000 inhabitants per day (DID). RESULTS: The collected data showed very high consumption of the antibiotic in Slovakia. Comparing to the published international data it was one of the highest consumers of antibiotics in Europe. The amount of packages used during the period 1998 - 2002 has decreasing tendency. Antibiotic usage expressed in DID showed moderate decrease. Consumption of macrolides was increasing during the studied period. Usage of drugs containing erythromycin and roxithromycin showed significant decrease. However, the usage of the drugs containing clarythromycin and azithromycin showed statistically important increase (p<0.001).Different therapeutic procedures were classified by pharmacoeconomical method of the cost - minimization analysis. CONCLUSIONS: According to the results of this analysis, the most effective treatment of tonsillitis was phenoxymethylpenicillin 15.30 SKK and penamecillin 18.50 SKK. Usage of these drugs for the treatment is efficient and economically convenient (p<0.001). According to the direct cost analysis, 52.2% of costs used for the treatment of tonsillitis was “wasted”. Wrong antibiotics were chosen in case of 58.5% of the patients.