OBJECTIVE: Even though Health-related Quality of Life (HRQL) instruments are increasingly being used, there is a lack of standardization of administration, interpretation, and understanding of cross-cultural issues. The objective of the International Health-related Quality of Life Outcomes Database (IQOD) program is to further the methodology of assessing conceptual equivalence of translated versions and apply this methodology to major HRQL questionnaires, such as the WHQ. METHODS: Hypothesized structure of the questionnaire as defined by its developer was first examined using principal component analysis (PCA) and multitrait analysis (MA). These analyses were performed on the original language version to test the hypothesized model. The model was then applied to each language version to evaluate any potential differences and to provide validation evidence of their psychometric properties. Data was collected from 4 studies (observational studies and clinical trials) in the UK, US, France, Germany, Italy, and Poland. The population consisted of 9023 peri, pre or post-menopausal women. RESULTS: The results of PCA and MA on country data showed that the hypothesized item grouping was not respected. In order to achieve conceptually equivalent translated versions, a new scoring was developed in collaboration with the developer. This new scoring was applied to the UK data using Confirmatory Factorial Analysis and showed that the model was correct (N=811, Chi2= 618.6, normed fit index (NFI)=0.89, goodness of fit index (GFI)=0.94). The same model was applied to the pooled sample and fit well (N=6047, Chi2= 5715.6, NFI=0.88, GFI=0.90). Calculation of Cronbach’s alpha (>0.70 for all countries) and evaluation of item convergent and divergent criteria showed good internal consistency and construct validity of the translated versions. CONCLUSION: The methodology used in this program can be applied to other questionnaires in evaluating cross-cultural equivalence and thus facilitating interpretation of multi-national studies.