OBJECTIVES: To evaluate the association between body mass index (BMI) and health-related quality of life (HRQoL) in a multiethnic Asian population in Singapore, and to explore if the World Health Organization (WHO) recommendation of alternative BMI cutoffs for Asians could be further strengthened by evidence of higher risk of impaired HRQoL using these criteria. METHODS: Consenting English, Chinese, Malay and Tamil-speaking primary care patients (age >or= 21 years) were interviewed using English/their respective mother tongue versions of the EQ-5D/EQ-VAS, Health Utilities Index (HUI2 & HUI3) and the SF-6D. We first evaluated the relationship between BMI and HRQoL (overall and individual attributes for each instrument) using multiple linear/logistic regression (where appropriate) to adjust for factors known to affect HRQoL. We next reorganized BMI into five categories (reflecting the differences in cutoffs between International/Asian classifications) and evaluated if median HRQoL scores were significantly different across these categories. RESULTS: Among 411 participants [response rate: 87%; median age: 51 years; obese: 19% (International); 33% (Asian)], after adjusting for sociodemographic and other factors, a tendency for underweight and obese subjects to report lower overall HRQoL scores was observed for most instruments. At the individual attribute level, obese subjects reported significantly lower HUI2 pain scores (regression coefficient: -0.035, P = 0.029) and greater odds of reporting problems for SF-6D role-limitations (odds ratio: 2.9, P = 0.005). Median overall HRQoL scores were not significantly different across the five BMI categories. CONCLUSION: Consistent with available studies, obese subjects reported worse HRQoL than normal-weight subjects. That underweight subjects also reported worse HRQoL is interesting and requires confirmation. HRQoL was similar in Asians using either WHO criteria.