OBJECTIVES: Health-related quality of life data are frequently collected in clinical studies from a number of countries and combined for analysis. This study compared AQLQ data across 16 countries (17 languages) to investigate if the measurement properties of the AQLQ are sufficiently consistent to support combining data in multinational trials. METHODS: The AQLQ data from the Gaining Optimal Asthma controL (GOAL) study was used for the analyses. Of 3416 patients treated, 1973 had an overall AQLQ score at baseline, 1850 at week 12  and 1832 at both.  The original language (North American English) was considered the reference language (RL).  Internal consistency, construct validity and responsiveness were evaluated for each translation. RESULTS: Number of patients completing each AQLQ language varied from 27 (Canadian French) to 256 (Mandarin Chinese) with 81 patients completing the RL. Mean age ranged from 31.7 years (Spain) to 52.9 years (Norway) and percent of males ranged from 30.3% (Brazil) to 74.4% (Norway). Cronbach’s alpha (baseline overall score) ranged 0.93 to 0.97 (RL 0.94). Correlation with baseline Asthma Control Questionnaire (ACQ) and with FEV1 were as expected ranging from -0.76 to -0.58 (RL -0.69) and -0.02 to 0.41 (RL 0.08) respectively.  Similarly, correlations with change from baseline for ACQ and FEV1 ranged from -0.83 to -0.61 (RL -0.78) and -0.11 to 0.56 (RL 0.03). The AQLQ showed ability to detect changes in ACQ over time in all languages except Danish. CONCLUSIONS: The finding that internal consistency, construct validity and responsiveness were consistent across languages and similar to the RL provides evidence of the quality of these translations and supports the combining of data for analyses.