To examine the association between the metabolic syndrome and C-reactive protein, fibrinogen, and leukocyte count, the author did a cross-sectional analysis of data from 8570 participants aged >/=20 years from the Third National Health and Nutrition Examination Survey (1988-1994). The metabolic syndrome was defined using criteria established by the Third Report of the National Cholesterol Education Program Expert Panel on Detection, Evaluation, and Treatment of High Blood Cholesterol in Adults. The age-adjusted prevalence of having an elevated C-reactive protein concentration was 29.0% (S.E.: 1.6%) for participants with the metabolic syndrome and 12.1% (S.E.: 0.6%) for participants without the metabolic syndrome (adjusted odds ratio (OR), 2.80; 95% confidence interval (CI): 2.36, 3.33). Compared with participants who had no abnormalities, the corresponding adjusted ORs were 1.91 (95% CI: 1.27, 2.87), 3.00 (95% CI: 1.96, 4.60), 5.01 (95% CI: 3.39, 7.41), 5.97 (95% CI: 3.83, 9.31), and 6.79 (95% CI: 3.55, 12.99) for participants with 1, 2, 3, 4, and 5 metabolic abnormalities, respectively. Participants with the metabolic syndrome had higher fibrinogen concentrations and white blood cell counts than those without this syndrome. Many people with the metabolic syndrome have a low-grade inflammation, which may increase their risk for future adverse events. A better understanding of the potential consequences of the high prevalence of low-grade inflammation among people with the metabolic syndrome is needed.