Neutrophil gelatinase-associated lipocalin (NGAL), a small 25 kDa protein strongly induced in injured renal tubular cells, represents an interesting emerging biomarker in the field of clinical nephrology. The aim of the present pilot study was to analyze circulating NGAL levels in a small cohort of 30 patients on chronic haemodialysis (HD), in order to assess any relationships with different laboratory and clinical parameters. Pre- and post-HD levels were higher in patients than in healthy subjects (485.2 +/- 49.7 vs 51.2 +/- 4.6 ng/mL; P < 0.001; and 167.4 +/- 48.0 vs 51.2 +/- 4.6 ng/mL; P = 0.01). Furthermore, a single HD session decreased NGAL levels by approximately fourfold (485.2 +/- 49.7 vs 167.4 +/- 48.0 ng/mL; p:0.01), with a reduction ratio of 73 +/- 14%. At baseline, direct and independent correlations were found between NGAL and, respectively, high-sensitivity C-reactive protein (beta = 0.34; P = 0.03) and spKt/V (beta = 0.35; P = 0.02). The findings showed that HD patients have chronically increased levels of circulating NGAL. However, with a single HD session, a marked reduction was achieved in circulating NGAL values, probably as a result of an important dialytic removal, similar to that observed for other cytokines. Finally, the direct independent correlation found between NGAL and spKt/V raises the question of whether, in the future, NGAL may also become a useful tool in predicting the adequacy of dialysis and in guiding the management of dialysis prescriptions.