OBJECTIVES: Measuring back pain for further clinical research required the linguistic validation of a nine-item questionnaire developed in US English. Based on the assumption that the original concepts were universally appropriate, we aimed to develop language versions of a US back pain questionnaire according to a rigorous methodology to ensure the conceptual equivalence between the original and the translations. METHODS: The process was conducted by a specialist in each target country using the following standardized methodology: 1) two forward translations by professional translators, native speakers of the target language and fluent in English; 2) comparison and reconciliation of the translations by the specialist in the target country and the translators; 3) backward translation by a native English speaker; 4) comparison of source and backward version; and 5) comprehension test on five individuals suffering from back pain and review by one clinician. RESULTS: Issues regarding the universal appropriateness of the original concepts emerged during the creation of the 35 language versions. Items investigating the respondent's ability to get in and out of his car had to be reformulated in countries where the ownership of cars was rare. Similarly for countries in which people did not wear socks or stockings an alternative question had to be found. CONCLUSION: The 35 language versions were established according to a rigorous translation methodology. The process ensured the conceptual equivalence of all language versions to facilitate the international comparison and pooling of data. This process also reveals that the original concepts are not necessarily universally appropriate. This indicates the necessity to integrate international feedback on concepts before the original questionnaire is finalized to facilitate the cross-cultural equivalence of concepts.