OBJECTIVE: Here we use a novel ELISA that is specific for full-length visfatin (PBEF/NAMPT), compare it with the existing C-terminal based assay and use it to investigate associations of visfatin with metabolic parameters. DESIGN, PATIENTS AND MEASUREMENTS: We established the specificity and effectiveness of the new ELISA and evaluated the associations of full-length visfatin with clinical, anthropometric and metabolic parameters in a cross-sectional study of 129 Thai subjects, consisting of 50 outpatients with type 2 diabetes and 79 healthy volunteers. RESULTS: The new ELISA accurately recovered full-length recombinant visfatin and detected visfatin secreted by primary human and rat adipocytes. We found serum full-length visfatin was significantly higher in subjects with diabetes compared to their nondiabetic peers (median 2.75 vs. 2.22 ng/ml, P = 0.0142). After adjustment for age, gender and traditional metabolic risk factors, adjusted mean visfatin remained significantly higher in the diabetes group (3.80 vs. 2.10 ng/ml, P = 0.0021). On Spearman univariate correlation analysis, visfatin was significantly associated with resistin (r = 0.30, P = 0.0011), but not with any other anthropometric or metabolic variables, including adiponectin multimers. On multiple linear regression analysis, the only covariates independently associated with visfatin were diabetes (t = 3.11, P = 0.0024) and log resistin (t = 2.68, P = 0.0086). CONCLUSIONS: Circulating visfatin is independently associated with diabetes and resistin concentration, but is not related to adiponectin multimers or other metabolic covariates. These data are suggestive of a potential role of visfatin in subclinical inflammatory states.