Cardiovascular diseases and type 2 diabetes are the major causes of mortality in Mexico. Metabolic syndrome (MS) is a cluster of factors that increase the risk to develop such diseases. Previous studies have shown that MS is associated with high tumor necrosis factor (TNF-α) levels. In fact, TNF-α has been proposed to be a useful marker for clinical diagnosis of inflammation at an early stage. Therefore, we analyzed TNF-α concentrations in Mexican individuals with or without MS and related these levels to the associated MS components. Clinical, anthropometric, and biochemical data were analyzed in 41 healthy and 39 MS individuals. Individuals were similarly grouped by age and gender.The serum TNF-α levels measured bya highly sensitive enzyme-linked immunosorbent assay (ELISA) kit were increased significantly in MS subjects compared with healthy individuals (P<0.001). The assay showed 78.1% sensitivity and 61.5% specificity with a cut-point level of 1.36 pg/mL. TNF-α levels higher than the cut-point value were correlated with insulin resistance indices. These findings support the hypothesis that serum TNF-α concentration could be a useful marker for early MS diagnosis. Nevertheless, we suggest the establishment of specific cut-point values in each studied population to evaluate potential clinical applications. J. Clin. Lab. Anal. 23:51–56, 2009. © 2009 Wiley-Liss, Inc.