• Demonstration of excessive enteric protein loss traditionally required the use of labeled macromolecules and prolonged stool collection uncontaminated by urine. α1-Antitrypsin (α1-AT) clearance has recently been used for the demonstration of enteric protein loss, but controversy still exists about the value of determining α1-AT concentration in random stool samples. We have measured α1-AT excretion in random stool samples from children with various gastrointestinal (GI) tract disorders using an immune nephelometric method. Statistically significant elevations in α1-AT concentrations were found in stools from patients with active celiac disease and confirmed PLE, while normal values were demonstrated in patients with irritable bowel and inactive celiac disease. We conclude that determination of α1-AT concentration in random fecal samples is an easy, reproducible screening method for the demonstration of excessive enteric protein loss in various GI tract disorders.