Background: Oxidative damage plays an important role in leading to major health-related events. The aim of this study was to assess the predictive value of a lipoprotein peroxidation marker, oxidized low-density lipoprotein (oxLDL) for incident mobility limitation (ML). Methods: Data are from 2985 well-functioning elders enrolled in the Health ABC study (median follow-up, 4.1 years). All oxLDL levels were measured at the baseline assessment. The oxLDL/LDL cholesterol (LDL-C) ratio (log value) was used as a measure of lipoprotein peroxidation. Mobility limitation was defined by 2 consecutive semiannual reports of any difficulty either walking 1/4 mile or climbing up 10 steps without resting. Severe ML was defined by 2 consecutive reports of great difficulty or inability to do the same tasks. Cox proportional hazards models were performed to assess hazard ratios (HRs) and 95% confidence intervals (CIs). Results: The mean (SD) age of the sample was 74.2 (2.9) years. After adjustment for potential confounders (sociodemographic factors, smoking, physical activity, body mass index, clinical conditions, biological markers, and medications), the relationship between the oxLDL/LDL-C ratio and disability events was statistically significant (per log-unit difference in the oxLDL/LDL-C ratio) (for ML: HR, 1.22; 95% CI, 1.06-1.41; for severe ML: HR, 1.43; 95% CI, 1.15-1.79). Consistent results were found when interleukin 6 level was included as a covariate in the adjusted models (ML: HR, 1.13; 95% CI, 0.98-1.31; severe ML: HR, 1.31; 95% CI, 1.05-1.64). No significant sex, race, interleukin 6 level, or clinical conditions interaction was found with the oxLDL/LDL-C ratio and mobility disability. Conclusions: Lipoprotein peroxidation predicts the onset of ML in older persons. The oxLDL predictive value for ML is partly explained by interleukin 6 levels. ©2005 American Medical Association. All rights reserved.