OBJECTIVE: The usefulness of the EQ-5D as a HRQoL measure in Asians with Parkinson's disease is not known. We therefore evaluated the validity and reliability of the EQ-5D in Singaporeans with Parkinson's disease. METHODS: English-speaking patients with Parkinson's disease were recruited from hospital clinics and through the Singapore Parkinson's Disease Society. Subjects completed a questionnaire containing EQ-5D and Parkinson's disease questionnaire (PDQ-39) twice in a 1-week period. Test-retest reliability was assessed for EQ-5D items, utility index and visual analog scale (VAS) using Cohen's kappa or intraclass correlation coefficients (ICC). Construct validity was assessed by examining Spearman's correlations between EQ-5D and PDQ-39 and measures of disease severity (Hoehn and Yahr stage, activities of daily living and motor sections of the unified Parkinson's disease rating scale (UPDRS) and the Schwab and England activities of daily living scale). RESULTS: Eighty-seven subjects (Chinese: 73, Malay: 3, Indian: 9, Eurasian: 2) completed baseline and 68 subjects completed follow-up questionnaires (median interval: 7 days). Kappa values exceeded 0.75 for all EQ-5D items except for anxiety/depression (kappa=0.58). ICC values were 0.78 and 0.83 for utility and VAS scores respectively. Correlation coefficients between utility and VAS scores and the PDQ-39 summary index were -0.66 and -0.45 respectively (p <0.001 for both). Both EQ-5D and PDQ-39 scores weakly correlated with most recent clinical ratings, e.g., correlation coefficients with the UPDRS activities of daily living scale were -0.29, -0.21 and 0.29 for EQ-5D utility, VAS and PDQ-39 summary index scores respectively. CONCLUSION: The EQ-5D appears to be a valid and reliable HRQoL measure for Singaporeans with Parkinson's disease.