Objective To build a simple,automatable detection method for diagnosing bacterial peritonitis. Methods Neutrophil gelatinase -associated lipocalin(NGAL),lactate dehydrogenase(LDH),proteins and glucose were assessed in peritoneal fluids from patients with nonmalignant ascites,along with nucleated cell count and differ-entiation.Results One hundred and eleven specimens were analyzed,26 of which with PMN count≥250 ×106 /L, thus compatible with bacterial peritonitis.The median concentration of LDH and NGAL was 3.4 and 3.7 -fold higher in samples with PMN≥250 ×106 /L.The concentration of proteins was also higher in samples with ≥250 ×106 PMN /L, whereas that of glucose was lower.The PMN count significantly correlated with peritoneal fluid values of LDH(r =0.859),NGAL(r =0.774)and proteins(r =0.268),but not with glucose(r =-0.069).The area under ROC curve was 0.88 for LDH,0.89 for NGAL and 0.94 for their combination(both tests positive),whereas that of proteins and glucose was 0.80 and 0.71,respectively.Sensitivities and specificities were 0.81 and 0.87 for LDH≥227U /L, 0.96 and 0.75 for NGAL≥120μg/L,0.77 and 0.95 for their combination.The agreement with PMN count was 0.86 for LDH,0.80 for NGAL,and 0.91 for their combination.Conclusion Assessment of NGAL in peritoneal flu-ids,especially in combination with LDH,may be a reliable approach for screening of bacterial peritonitis in patients with nonmalignant ascites.