We have studied a patient from a family in which 17 male infants died in the first years of life. The clinical characteristics of this disorder were established from information from eight patients. The features included diarrhea, diabetes mellitus, hemolytic anemia, eczematoid rashes, and exaggerated responses to viral illnesses, combined with pathologic evidence of autodestruction of endocrine glands, insulitis, and thyroiditis with thyroid autoantibodies in one patient. When tested, B-lymphocyte cell function, T cell numbers, polymorphonuclear leukocyte chemotaxis, and complement concentrations were normal. Lymphocyte stimulation with phytohemagglutinin was low in one to two affected males and delayed skin test anergy was noted in another, raising the question of a T-lymphocyte cell abnormality. The basic genetic mechanism is unknown, but involvement of an immune response locus on the X chromosome, dysfunction of which is responsible for overactivity of the autoimmune system, is postulated.