This a report of a family of two sibships resulting from consanguineous matings of first cousins once removed. Eight of 28 children in the two sibships were affected by edema, growth retardation, diarrhea, abdominal pain, or clubbing, in varying combinations. In 4 patients, ascites developed and all 4 died. Autopsies performed in 2 of the cases revealed hepatic vein stenosis which caused a Budd-Chiari syndrome. Laboratory examinations revealed iron-deficiency anemia and low serum albumin and globulin in all affected family members. In some cases, mild eosinophilia was present. All patients had normal lymphocyte counts. Five patients were investigated in detail, and a protein-losing enteropathy was demonstrated. In some patients, the intestinal biopsy showed slight to marked dilation of mucosal lymphatics. Lymphangiography was normal in all 5 cases, and 3 patients formed antibodies in response to immunization with TAB vaccine. Three patients were treated with prednisone. In 2 cases, abdominal pain and edema disappeared, and the patients gained a considerable amount of weight. Serum proteins returned to normal levels in all 3 prednisone-treated patients, their polyvinylpyrrolidone excretion decreased, and the parameters of protein metabolism returned to normal in the 1 patient in which they were reinvestigated. The cause of this familial protein-losing enteropathy is unknown.