Increased levels of neutrophil gelatinase-associated lipocalin (NGAL), a small 25-kd stress protein released by several injured cells, have been reported in different pathological conditions such as kidney and chronic inflammatory bowel diseases. As NGAL is also emerging as a biomarker for monitoring the response to different types of treatment, the aims of this pilot study were to analyze urinary NGAL levels in a small cohort of patients affected by Crohn disease and to evaluate the eventual impact of the intravenous administration of infliximab on these levels. Crohn disease patients presented increased NGAL values compared with controls (210.5 ng/mL [88.3-1100.0 ng/mL] vs 7.6 [4.4] ng/mL; P = 0.001); the infusion of a single high dose of infliximab induced an impressive reduction in these levels to 80.1 ng/mL (38.6-400.2 ng/mL; P = 0.006) with a mean reduction ratio of 62.1%. These findings suggest a pivotal role of NGAL in the systemic adaptations to Crohn disease, also confirming the potential usefulness of NGAL measurement in the evaluation of early responses to therapy or in predicting different clinical outcomes.