OBJECTIVES: The VAS is a common response scale in PRO questionnaires, which are used in multinational studies from which data is pooled.  This study was designed to evaluate the suitability of VAS for use in different international settings, specifically to evaluate the cognitive processes and challenges occurring when respondents from a range of countries/cultures complete VAS. METHODS: Adults were recruited from: UK; Mexico; Spain; Malaysia; India; South Africa, with approximately 50:50 males/females and higher/lower education split.  Each completed four VAS followed by a cognitive debriefing interview, once before and once after receiving standardized instructions. RESULTS: Thirty-seven lay persons were interviewed across 6 countries, mean age was 46 ±19; 51.4% were male. Several respondents commented on the unfamiliar style of the VAS.  Some reported the anchors as inappropriate/ambiguous, impeding scale completion, or that anchor wording caused them to avoid scale extremities.  Respondents noted the lack of intermediate markers on the VAS, therefore having to rely on ‘guesswork’: most used quantitative rather than qualitative strategies when deciding where to place their mark. Some had concerns that ‘guesswork’ led to inaccurate responses. British and Spanish respondents used principally quantitative methods whereas Zulu speakers relied more on qualitative techniques. Respondents from Malaysia, South Africa and India were more inclined to report challenges; Zulu and Tamil speakers completed the VAS in the least conventional way. CONCLUSIONS: The study provides substantial evidence that the use of VAS in different international settings will result in data which has been influenced by differences in interpretation of the scale, providing support for the FDA’s perspective that VAS can provide a ‘false sense of precision’.  This has implications for international clinical trials in which data pooling is required.  This study allowed for a critical appraisal of the VAS response format which will assist in the collection of more valid data in multinational studies.