OBJECTIVES: In a pharmacoeconomic analysis, price differences between drugs in a country should be taken into consideration. In addition there are situations where medicines have the same indication are priced differently. In applying the result of analysis made overseas to Japan, we should also take into account not only of different prices from country to country but also of differences in the pricing method among countries. Thus, in this study, we compared the differences in drug prices among selected countries and examined the methodology for an international comparison of drug prices. METHODS: Using the ViDAL (France), Rote Liste (Germany) MIMS (UK) and NHI price list (Japan), we compared the average daily costs at the time of the introduction of the brand name drugs of antihypertensive agents (ARB, ACE), statins, PPI, and antidepressants (SSRI, SNRI), in France, Germany, the UK and. Japan We adopted the WHO-DDD as the average daily dose and converted the drug prices into euros. We not only compared drug prices directly but also examined the price range of drugs having the same efficacy. RESULTS: The drug price differed from country to country according to the efficacy; while statins and PPI were most expensive in the U.K., the price of SSRI was the highest in France. The variation in price of drugs with the same efficacy was greater in Japan; supposing the price of the cheapest drug in each therapeutic group to be 1, that of the most expensive drugs was 3.0 for ARB, 4.1 for statins, 2.5 for PPI and 8.3 for SSRI, which were on higher levels than those in other countries. CONCLUSIONS: Our study suggested that variation in the price of drugs with the same efficacy might greatly affect pharmacoeconomic analyses.