PURPOSE: The link between hyperuricemia and insulin resistance has been noted, but the prevalence of the metabolic syndrome by recent definitions among individuals with hyperuricemia remains unclear. Our objective was to determine the prevalence of the metabolic syndrome according to serum uric acid levels in a nationally representative sample of US adults. METHODS: By using data from 8669 participants aged 20 years and more in The Third National Health and Nutrition Examination Survey (1988-1994), we determined the prevalence of the metabolic syndrome at different serum uric acid levels. We used both the revised and original National Cholesterol Education Program Adult Treatment Panel (NCEP/ATP) III criteria to define the metabolic syndrome. RESULTS: The prevalences of the metabolic syndrome according to the revised NCEP/ATP III criteria were 18.9% (95% confidence interval [CI], 16.8-21.0) for uric acid levels less than 6 mg/dL, 36.0% (95% CI, 32.5-39.6) for uric acid levels from 6 to 6.9 mg/dL, 40.8% (95% CI, 35.3-46.4) for uric acid levels from 7 to 7.9 mg/dL, 59.7% (95% CI, 53.0-66.4) for uric acid levels from 8 to 8.9 mg/dL, 62.0% (95% CI, 53.0-66.4) for uric acid levels from 9 to 9.9 mg/dL, and 70.7% for uric acid levels of 10 mg/dL or greater. The increasing trends persisted in subgroups stratified by sex, age group, alcohol intake, body mass index, hypertension, and diabetes. For example, among individuals with normal body mass index (<25 kg/m2), the prevalence increased from 5.9% (95% CI, 4.8-7.0), for a uric acid level of less than 6 mg/dL, to 59.0%, (95% CI, 20.1-97.9) for a uric acid level of 10 mg/dL or greater. With the original NCEP/ATP criteria, the corresponding prevalences were slightly lower. CONCLUSIONS: These findings from a nationally representative sample of US adults indicate that the prevalence of the metabolic syndrome increases substantially with increasing levels of serum uric acid. Physicians should recognize the metabolic syndrome as a frequent comorbidity of hyperuricemia and treat it to prevent serious complications.