There are a lack of data on the quantity and location of eosinophils in the gastrointestinal tract of healthy individuals. Accordingly, we examined gastrointestinal biopsies obtained during endoscopic evaluation of pediatric patients. Biopsies were previously interpreted as having no diagnostic abnormality. The presence of extracellular eosinophil constituents and the quantity of eosinophils in atopic versus nonatopic individuals was determined. In the esophagus, eosinophils were present in only 2.7% of high-power fields (hpf), with a mean value of 0.03+/-0.10 eosinophils/hpf (mean+/-standard deviation) and a maximum of 1 eosinophil/hpf. Examination of the antrum and fundus revealed similar numbers of eosinophils in the lamina propria (1.9+/-1.3 and 2.1+/-2.4 eosinophils/hpf, respectively), with no eosinophils observed in the surface epithelium. In the small intestine, there were 9.6+/-5.3 (maximum, 26 eosinophils/hpf) and 12.4+/-5.4 eosinophils/hpf (maximum, 28 eosinophils/hpf) in the intercryptal lamina propria of the duodenum and ileum, respectively. The number of eosinophils in the surface epithelium and crypt epithelium was minimal. In the large intestine, the highest concentration of eosinophils was observed in the cecum (20.3+/-8.2 eosinophils/hpf; maximum, 50 eosinophils/hpf), and there were lower concentrations in the transverse and sigmoid colon (16.3+/-5.6 and 8.3+/-5.9 eosinophils/hpf, respectively). The percentage of fields demonstrating extracellular eosinophil granules in all gastrointestinal segments was 70% to 93%, and extracellular granules were most numerous at the edge of the biopsy (P<0.05). Atopic and nonatopic patients had comparable numbers of eosinophils. These data establish baseline gastrointestinal eosinophil values in pediatric patients without apparent pathological disease.