Small bowel permeability was investigated in 87 children with recurrent abdominal pain by measuring the 24-h urinary excretion of orally administered 51Cr-EDTA. The mean excretion was 3.64% +/- 1.49% per 24 h. The difference between the mean urinary excretion in children with recurrent abdominal pain and control children (2.51% +/- 0.70%), was significant (p less than 0.01, two sample t-test). The increased small bowel permeability in children with recurrent abdominal pain might indicate an intestinal etiology for the patients' complaints.