OBJECTIVES: Prior to use in an international study involving HIV patients, the original 20-item Symptoms Distress Module (SDM), underwent linguistic validation in 25 languages. The original scale was developed in US English by the Adult AIDS Clinical Trials Group to assess the impact of common HIV-related symptoms (either due to HIV disease or its treatments). A rigorous methodology was required to ensure conceptual equivalence and cultural relevance across different languages. METHODS: The translation process was conducted by a specialist in each target country using the following standardized methodology: 1) two forward translations by professional translators who were 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) back-translation by a native English speaker; 4) comparison of source and backward version; 5) review by a clinician; and 6) comprehension test on five individuals with HIV/AIDS. RESULTS: The translation process revealed two major challenges. First, for items which contain two different terms to describe one single concept, some languages only have one word that suitably conveys the concept. Second, the comprehension tests revealed that in countries where people are less used to completing questionnaires, the instructions "The questionnaire...should take no more than five minutes to complete" were perceived as stressful. This required alternative wording. CONCLUSION: The 25 language versions of the SDM were established according to a rigorous standardized translation methodology. The process aims to ensure conceptual equivalence across language versions to facilitate international comparison and pooling of data. The linguistic validation process as a whole supports the integration of international feedback on concepts and wording during the development of questionnaires.