OBJECTIVES: Translation of patient reported outcomes (PRO) measures is an essential component of research methodology in preparation for multinational clinical trials. One such measure is the FACT-Leukemia questionnaire (FACT-Leu), which evaluates the quality of life (QOL) of leukemia patients. METHODS: This study set out to linguistically validate the FACT-Leu for use in Argentina, Austria, Belgium, Bulgaria, Canada, Chile, China, Croatia, Czech Republic, Denmark, Egypt, Finland, France, Germany, Greece, Hungary, India, Israel, Italy, Japan, Korea, Latvia, Lithuania, Malaysia, Mexico, Netherlands, Norway, Poland, Romania, Russia, Serbia, Slovak Republic, Slovenia, South Africa, Spain, Sweden, Taiwan, Thailand, Turkey, Ukraine and Venezuela. The study sample consisted of 758 patients (444 males/310 females/4 missing) diagnosed with leukemia. Patient mean age was 47 years, and at the time of administration, 628 patients were receiving medical treatment. The sample consisted of patients who speak 43 languages collectively. The FACT-Leu was translated according to the standard FACIT methodology. Patients diagnosed with Leukemia completed the respective translated questionnaire and then participated in a cognitive interview to determine if there were any problems with the translations or item content. Quantitative analyses (descriptive statistics and reliability analyses) were performed on the combined sample and participant comments were analyzed qualitatively in order to confirm the validity of the translations. RESULTS: The FACT-Leu translations exhibited good internal reliability and linguistic validity. The alpha coefficient for the questionnaire as a whole including all languages was 0.96. Subscale alphas ranged from 0.81 to 0.91, also indicating good internal consistency. All items on the FACT-Leu correlated at an acceptable level. CONCLUSIONS: The FACT-Leu demonstrated acceptable reliability and linguistic validity in all 43 languages. We consider these translations acceptable for PRO assessment in international research and clinical trials.