OBJECTIVE: Although assessment of health-related quality of life (HRQOL) as an outcome in multi-center clinical trials is common, little is known about inherent international patient differences. Thus, we sought to evaluate the effects of nationality in an international post-MI population. METHODS: In the GUSTO-I Angiographic Trial, 1848 patients (pts) from 10 countries were contacted for HRQL telephone interviews 2 yrs post infarct (87.7% response). Questionnaires translated (forward/backward) into French, Dutch, German, and Spanish measured physical function (Duke Activity Scale), emotional function (Minn Living with Heart Failure), social function and perceived health (MOS SF-36), and symptoms (angina and dyspnea). Nationality was coded as US, Canada (CN), Australia (AU), and Europe (EU). Structural equation modeling (SEM) was used to evaluate nationality's effect on HRQL, symptoms, and disease severity. RESULTS: At baseline, US pts had significantly more comorbidity than CN pts and more revascularization procedures than the other patients groups. In univariate analyses, no differences among nationalities were present in any HRQL outcomes. In the SEM (which controlled for disease severity and symptoms) nationality did not have a significant impact on HRQL, despite EU pts reporting more angina and dyspnea than US pts (p<0.0001) and more dyspnea than CN pts (p<0.001). CONCLUSION: In this sample of homogenous post MI pts from similar Westernized cultures, nationality did not impact HRQL. Although differences may exist in more heterogenous samples, these findings suggest that pooling similar Westernized cultures' outcome data is valid.