A patient is reported with a malabsorption syndrome associated with nodular lymphoid hyperplasia of the small intestine and dysgammaglobulinemia characterized by virtual absence of IgA and IgM, with a reduced concentration of IgG. Prominent clinical features were severe steatorrhea and tetany. The low serum calcium and transient mild hyperphosphatemia suggested parathyroid hypofunction, but studies of calcium metabolism did not substantiate this diagnosis. The degree of hypocalcemia seemed dependent upon the severity of the steatorrhea. Evidence of early osteomalacia probably reflected an associated Vitamin-D deficiency. Investigation failed to reveal the cause for steatorrhea, and the pathogenesis of malabsorption seen in patients with dysgammaglobulinemia remains undefined.