The aim of this study was to evaluate the relationship between serum levels of beta-trace protein (BTP), a low molecular weight (MW) protein, and glomerular filtration rate (GFR). GFR and serum levels of BTP, and for comparison creatinine (Creat), cystatin C (Cys) and beta 2-microglobulin (beta 2M), were measured in 60 patients, with renal function ranging from normality to advanced renal failure. Serum levels of BTP progressively increased with the reduction of GFR. A good correlation was found between GFR and serum levels of BTP (r=0.918), Creat (r=0.932), Cys (r=0.937), and beta 2M (r=0.924). Furthermore, no statistically significant difference was found between BTP and Creat, Cys, beta 2M, as indicators of a moderate GFR impairment. These preliminary data indicate that BTP might be suitable as an indicator of GFR.