Introduction With the growing use of Patient-Reported Outcomes (PROs) questionnaires for the evaluation of medicines in Europe, the need for international measures has increased. In response to European regulators' concerns about the methodology used to achieve cultural adaptation of PRO measures, the ERIQA Group and Mapi Research Institute have investigated current guidelines. OBJECTIVES: To identify and review the methods used for cultural adaptation of PRO measures, to propose recommendations of best practice to European regulators. METHODS: Relevant papers were identified from Medline, Embase, and Mapi Research Institute's database. The databases were explored with "quality of life", "questionnaires", "health status indicators" matched with "translating", "cross-cultural comparison", "translations issues" and "cross-cultural research". Papers published between January 1966 and April 2001 were considered. 415 abstracts were reviewed. Papers were included if they proposed guidelines or recommendations and/or they reviewed and criticised methods. RESULTS: Thirty-two papers met the inclusion criteria. We identified 14 sets of guidelines. The review highlighted a lack of consensus regarding the terminology to qualify the process of adapting a PRO measure from a source to a target language, and the scope covered by this terminology. Common points included multiple forward translations, reconciliation sessions, some form of back-translations and psychometric validation. Differences were seen in the importance given to back-translation, focus groups, cognitive debriefing, and recruitment criteria for translators. With only two articles comparing methodologies, the review could not determine the best method to apply among the 14 identified. CONCLUSION: This review demonstrates disparity in definitions and methods. There is no evidence proving that one method leads to better results than another. We propose providing regulators with an overview of what most investigators recommend as minimum requirements. This proposal will be presented in the form of a checklist including a maximum of 12 steps from concept definition to psychometric evaluation, depending on the target culture and/or language and type of PRO.