OBJECTIVE: To elaborate a useful level of detail according to measurement and valuation of costs associated with rheumatoid arthritis. METHODS: Unit costs - comprehended as multiplicative part of costs as product of amount and price - have a substantial impact on health economic evaluations. Performing an intensive Internet research we assessed country-specific unit costs for the ten cost domains doctor visit, medication, diagnostic procedures, monitoring, hospitalization, rehabilitation, personal help, stoppage, traveling and other treatments. The most differentiated cost domains were rheumatic medications(65 cost items) and monitoring (25 cost items). We reported the type of cost item, country, total costs of one unit, name of data source, date of data, homepage address, date of review, calculation assumption and calculation method. The evaluation was performed for Australia, Canada, France, Germany, and Great Britain. All unit costs were given in national currency as well as US$ for comparative purpose. RESULTS: Significant differences in values of unit costs were identified with the Internet research. The country-specific values of comparative unit costs differed a lot. England and Australia show high differences of unit cost values per type of doctor visit. All five countries have high variances within the different diagnostic procedures, the kind of personal help and the type of traveling. The most differentiated references for the evaluation of medication costs were found in Germany. CONCLUSION: In general the identification of unit costs therefore has to adapt the specific payment systems of health care. It is non-permissible to transfer country-specific results to other countries. Because the amount of unit costs differs a lot, each health economic study report has to explain the used calculation approach. Otherwise the user is unable to prove the robustness of data. Additionally the performance of sensitivity analysis is aggravated.