Five infants from three families died between the ages of 2 and 7 months with venocclusive disease of the liver. No dietary, toxic, or other extrinsic cause was uncovered. In one family the first infant was breast-fed; the second one received no breast milk. In two of the families the parents were cousins. All infants had some evidence of immune deficiency, including hypogammaglobulinemia in at least three, multiple infections especially Pnumocystis carnii and enteroviruses, and lymphoid tissues devoid of germinal centers and mature plasma cells. Other findings in some of the infants, not previously recorded in venoocclusive disease, were microcephaly, multiple small cerebral softening, and left atrial endocardial fibrosis. A congenital cause for venoocclusive disease is suggested in these cases.