OBJECTIVE - To assess the prevalence in HIV-infected patients of the metabolic syndrome as defined by the National Cholesterol Education Program, i.e., three or more of the following components: abdominal obesity, hypertriglyceridemia, low HDL cholesterol, high blood pressure, and high fasting glucose. RESEARCH DESIGN AND METHODS - In this cross-sectional study, 710 HIV-infected patients managed at the outpatient clinic of a tertiary hospital during 2003 completed the study protocol consisting of a medical examination and laboratory analysis after a 12-h overnight fast. RESULTS - Metabolic syndrome prevalence was 17% and increased from 5.1% among HIV-infected patients under age 30 years to 27.0% for those aged 50-59 years. Age (per 10-year increment) (odds ratio [OR] 1.41 [95% CI 1.12-1.77]), BMI (1.27 [1.19-1.36]), past and present protease inhibitor exposure (2.96 [1.03-3.55] and 4.18 [1.4-12.5], respectively) were independently associated with the metabolic syndrome on logistic regression analysis. Furthermore, only stavudine (d4T) (1.74 [1.01-2.98]) and lopinavir/ritonavir (2.46 [1.28-4.71]) were associated with the metabolic syndrome after adjustment for age and BMI. CONCLUSIONS - The prevalence of metabolic syndrome among these HIV-infected patients is similar to that previously reported in uninfected individuals. Of specific concern is the association of protease inhibitor exposure with the metabolic syndrome and, more specifically, with exposure to stavudine and lopinavir/ritonavir when individual antiretroviral drugs were analyzed.