Background: High sensitivity C-reactive protein (CRP) is a marker of acute inflammation recently recognized as an independent predictor of future cardiovascular disease and diabetes. The identification of modifiable factors, such as diet, that influence serum CRP concentrations may provide the means for reducing the risk of these diseases. Data on longitudinal associations between dietary fiber intake and CRP are currently lacking. Objective: The purpose of this study was to examine longitudinal associations between dietary fiber intake and CRP. Design: Data collection took place at baseline and quarterly (every 13 wk) thereafter for a total of 5 visits, each including measurements of body composition, CRP, diet, and physical activity. Relations between serum CRP and dietary fiber were assessed by using linear mixed models and logistic regression, adjusted for covariates. Results: A total of 524 subjects had multiple measurements of CRP and dietary factors. The average total dietary fiber intake was 16.11 g/d. Average serum CRP was 1.78 mg/L. We observed an inverse association between intake of total dietary fiber (separately for soluble and insoluble fiber) and CRP concentrations in both crosssectional and longitudinal analyses. The likelihood of elevated CRP concentrations was 63% lower (OR: 0.37; 95% CI: 0.16, 0.87) in participants in the highest quartile of total fiber intake than in participants in the lowest quartile. Conclusions: Our results suggest that dietary fiber is protective against high CRP, which supports current recommendations for a diet high in fiber. © 2006 American Society for Nutrition.