Two children with primary intestinal lymphangiectasia (PIL) are presented, both of whom had been prescribed an MCT supplemented diet low in long chain fatty acids. The hypoproteinemic edema improved in one patient, but persisted in the other. Following several years of dietary therapy, both subjects were re-evaluated, and a duodenoscopy and radiography of the digestive tract were performed. The duodenoscopic procedure evidenced two types of lymphangiectatic plaques on the surface of the duodenal mucosa: one form had a diameter of less than 1 mm, while the other exceeded 3 mm. The smaller lesions were seen in the child with the more favorable clinical course, whereas both types were observed in the other patient. Radiological examination disclosed the typical anomalies of intestinal lymphangiectasia only in the subject who had not responded to the dietary regimen. These results suggest that endoscopy affords a more precise assessment of the anatomic injury and could play an important role in formulating an accurate clinical diagnosis.