OBJECTIVE: The metabolic syndrome is associated with a high risk of diabetes and cardiovascular disease, and Hispanics in the United States have higher rates than do other ethnic groups. We assessed the prevalence of the metabolic syndrome and its individual components in Puerto Rican adults. METHODS: We conducted a cross-sectional study that used a probability cluster design to select a sample of households of the San Juan metropolitan area from 2005 through 2007. A total of 859 persons aged 21-79 years completed a face-to-face interview, blood pressure and waist circumference measurements, and blood sampling. Our primary outcome measure was metabolic syndrome as defined by the updated NCEP-ATP criteria. RESULTS: Prevalence of the metabolic syndrome was 43.3%; 45.3% for men and 42.2% for women (P>.05). Prevalence significantly rose with age, from 12.8% among participants aged 21-29 years to 58.2% for participants aged 70-79 years (P<.001). Corresponding increases in the prevalence of the metabolic syndrome in both men and women were also observed; the prevalence peaked in men aged 50-59 years (62.6%) and in women aged 70-79 years (65.2%). Elevated glucose (49.8%) and abdominal obesity (49.0%) were the most common components of the metabolic syndrome, followed by elevated blood pressure (46.1%), reduced high-density lipoprotein cholesterol (46.0%), and elevated triglycerides (31.3%). Substantial variations were found between men and women in the prevalence of individual components. CONCLUSIONS: Puerto Ricans have a high prevalence of the metabolic syndrome. This health disparity has implications for diabetes and cardiovascular prevention programs.