OBJECTIVES: To culturally adapt the Hepatitis Quality of Life Questionnaire (HQLQ) and assess its suitability for use in English-speaking hepatitis B virus infected (HBV) patients in Singapore. METHODS: Two patient focus groups were conducted to facilitate the cultural adaptation of the HQLQ, a disease-targeted, multi-item scales HRQoL questionnaire. Reliability was assessed using Cronbach's alpha coefficients (for internal consistency) and intraclass correlation coefficients (for test retest reliability). Item-to-scale correlation (corrected for overlap) was assessed using Spearman's rank correlations (?) between scale scores and their constituent items. For known-groups validity, statistically significant differences in all scale scores among different categories of HBV patients, namely asymptomatic carrier, chronic hepatitis B, compensated cirrhosis, decompensated cirrhosis, hepatocellular carcinoma and post-liver transplants were tested using one-way ANOVA. Healthy volunteers with no significant disease from the general population were recruited as controls. Convergent and divergent construct validities were tested in 10 and 14 a priori hypotheses respectively and the correlations were assessed using Spearman's rank correlation coefficients (?). RESULTS: The culturally adapted questionnaire was tested in 298 HBV patients. The reliability coefficients were excellent with a>0.7 for all scales and acceptable correlation coefficients were obtained for 10 of the 12 scales. Item-to-scale correlations were good with most items highly correlated with their hypothesized scales. For known-group validity, a comparison of mean scores at different stages of the disease showed significantly lower HRQoL scores in cases of more advanced stages of disease in most scales. Convergent and divergent construct validities were supported by the presence of hypothesized correlations between the HQLQ and the EQ-5D domains (8 of 10 hypotheses for convergent construct validity and all hypotheses for divergent construct validity were fulfilled). CONCLUSION: The culturally adapted HQLQ has good validity and reliability, making it a potentially useful outcome measure in the evaluation of HBV patients in Singapore.