Jejunal endoscopy and histopathological study of biopsied specimens were performed to clarify states of jejunal mucosa and the mechanism of enteric protein loss in six patients with protein-losing enteropathy, including four patients with intestinal lymphangiectasia, one patient with constrictive pericarditis associated with dilated lymphatics of the intestine, and one patient with Budd-Chiari syndrome. Three cardinal endoscopic findings, scattered white spots, white villi, and chyle-like substances covering the mucosa, were demonstrated in protein-losing enteropathy. Scattered white spots indicated markedly dilated lymphatics in the stroma of the villi. White villi seemed to be due to fats including chylomicrons or fat droplets in the absorptive cells, interepithelial spaces, and/or stroma, even though the biopsies were obtained in the fasting state. Therefore, white villi suggest impaired transport of fats from intestinal epithelial cells to intestinal lymphatics. These three cardinal findings are thought to be characteristic for protein-losing enteropathy secondary to lymphatic disorders.