OBJECTIVES. Although personality is known to influence patients' self-ratings of health, its effects on reports of health-related quality of life (HRQOL) have not been fully described. We examined the relationship between a dimension of personality called negative affectivity (NA;a general disposition to experience negative mood states) and HRQOL, controlling for age and common chronic physical and mental diseases. METHODS. We used data from 3 samples of veterans: the Department of Veterans Affairs (VA) Normative Aging Study (NAS), the Veterans Health Study (VHS), and the VA Women's Health Project (VA WHP). For each of the 8 SF-36 scales and the physical and mental component summary scales, 2 regression models were estimated, the first of which included only chronic diseases and age and the second of which added NA. RESULTS. NA was consistently negatively associated with SF-36 scale scores in bivariate analyses. The regression models indicated that across the 3 samples, NA explained between 0% and 13.9% additional variance in the scales, with the least additional variance in the physical function domains (range 0-2.6%) and the most in the mental function domains (range 0-13.9%). Results from the summary scales were similar: NA explained none of the variance in the physical component summary and 3.5% to 10.4% in the mental component summary. These results were largely consistent across the 3 samples. CONCLUSIONS, These results suggest the importance of NA in patients' ratings of HRQOL-beyond that of age and chronic conditions. Thus, clinicians and researchers who rely on measures such as the SF-36 to assess health status should consider that personality, as well as underlying health, can affect self-ratings of HRQOL,