Policy analysts summarize health-related quality of life (HRQL) with a single value representing the 'worth of life' arising from the many dimensions of HRQL. OBJECTIVES: To: (1) examine construct validity of two summary HRQL measures, a visual analogue scale (VAS) and EuroQol preference weights (PW), in Parkinson's Disease (PD) patients and (2) predict PW and VAS scores from a HRQL profile measure. METHOD: In a cross-sectional survey of 193 neurology questionnaires contained: the Medical Outcomes Study 36-item short form (SF-36), PD stage and symptoms, VAS, EuroQol, and health satisfaction. A priori hypotheses for testing construct validity predicted varying strengths of relationships between the summary HRQL scores and the SF-36, clinical, and health satisfaction scores. RESULTS: The correlation between VAS and PW was moderate (Spearman correlation 0.415). The PW had more ceiling scores than the VAS (19% vs. 2%). The ranked order of correlation between the individual SF36 scale scores, the clinical scores and the VAS was as hypothesized, but that for the PW was not. Specifically, the General Health scale ranked 1 for the VAS but 7 for the PW; Health Satisfaction ranked 4 for the VAS but 13 for the PW. The VAS distinguished mild from moderate stage subjects while the PW did not. Models predicting VAS and PW scores from SF-36 scores had adjusted model R-squares of 0.44 (VAS) and 0.52 (PW). CONCLUSION: The VAS, but not the PW, distinguished subjects with different disease severity. The two measures were only moderately correlated and had very different relationships with the domains of HRQL, particularly general health perceptions and health satisfaction.