The glycoprotein lactoferrin is found in many body fluids but also in the granules of neutrophilic granulocytes. Fecal lactoferrin levels increase quickly with the influx of leukocytes into the intestinal lumen during inflammation. This biomarker has recently been shown to be a sensitive and specific marker of disease activity in chronic inflammatory bowel disease. Our aim was the determination of fecal lactoferrin as a marker of intestinal inflammation and therapeutic response following infliximab therapy in pediatric patients with Crohn's disease (CD). A total of five patients (ages 10-15 years) with severe Crohn's disease as defined by the Pediatric Crohn's Disease Activity Index (PCDAI) was enrolled in the study. The fecal lactoferrin levels were determined before and after therapy with infliximab by a quantitative lactoferrin ELISA (IBD-SCAN; TechLab, Inc.). Of the five patients on infliximab therapy, three received a single infusion and the remaining two underwent a regime with three maintenance infusions. All five patients responded to infliximab clinically after the first infusion, and in all patients, fecal lactoferrin levels significantly and rapidly decreased from elevated to near baseline in parallel to clinical assessment and the PCDAI. The reduction in fecal lactoferrin at days 7-10 was 93.43 +/- 4.49%, in comparison with the level before infliximab therapy, and correlated with a mean decrease in the PCDAI from 48.50 to 14.0. For the patients followed during multiple infusions, one remained with mild disease and the other reached remission (subjective and PCDAI). Fecal lactoferrin is a sensitive and specific biomarker representing intestinal inflammation and response to therapy in pediatric patients with Crohn's disease. It may be a helpful noninvasive diagnostic tool for monitoring therapeutic efficiency in pediatric IBD patients. Future studies are needed to further establish the relationship between endoscopic changes and the level of fecal lactoferrin as well as the possible role of lactoferrin as being an early and preclinical indicator of relapse.