Background: This study identifies and compares the individual cost components of hospital and ambulatory services that manage the care of hypertensive patients in eight countries: the US, the UK, France, Spain, Germany, Italy, Canada and Australia. Methods: Hypertension-related costs are classified according to four major cardiovascular events: (i) acute myocardial infarction; (ii) congestive heart failure; (iii) stroke; and (iv) renal failure, which was subdivided into renal failure treated by dialysis and renal failure treated by kidney transplantation. To make cross-country costs comparisons, we used the DRG codes used in the US and ERG-like codes from each country. US cost information was obtained from hypertension data available from the literature and health economics researchers. For costs in other countries, we consulted with national health economics experts in each country, used analyses by the Research Triangle Institute, and performed Medline and international literature searches. When available, we obtained information from the countries' public and private nationally representative data sources. For cross-country currency adjustments, all currencies were converted using the Purchasing Power Parities from the Organisation for Economic Cooperation and Development, and then converted into inflation-adjusted year 2000 US dollars. Results: There exists considerable variation in hypertension-related costs from multinational clinical studies. This study documents that costs are generally higher in the US than in other countries; however, this is not always true. In particular, costs of treating heart failure in France and the costs of renal failure without transplantation in Germany and the UK are relatively high. Discussion: While analysing multinational hypertensive cost data, this study also addresses the impact of cross-country cost variations on cost analyses. During the last decade, drug-development researchers have drawn extensively upon multinational trials to resolve enrolment problems and drug-registration issues. At the same time, formulary decision-makers are increasingly demanding multinational cost-effectiveness analyses of the clinical differences found between drug-treatment regimens. Since these data are typically not captured by randomised clinical trials, standard cost estimates must be applied to the clinical trials' resource data, although such standardised calculations do not necessarily account for clinical and cost variations between countries. Conclusion: This paper serves as an instrument for identifying which national and event cost data are comparable for analysis as well as highlighting specific problem areas for cost data integration. Although the study focuses on hypertension-related costs, its results may provide insight for multinational cost comparisons of other diseases where similar hospitalisation costs may be analysed.