Sixteen of 77 patients (21 percent) with common variable immunodeficiency or IgG subclass deficiency contracted non-A, non-B hepatitis in association with intravenous infusions of immunoglobulin. The hepatitis seemed to run a more severe course in these patients than in non-immunodeficient patients. Twelve patients had clinical symptoms, and five died with hepatitis being the cause of death in two and a contributing factor in three. Liver biopsy specimens showed early chronic active hepatitis and cirrhosis. In addition to increases in liver enzymes, 13 patients had increases in alkaline phosphatase levels. All but two patients who contracted hepatitis had been given 50 mg/kg per week or more of intravenous immunoglobulin. Lymphocyte counts, T/B cell ratios, and T-lymphocyte function did not differ between those in whom hepatitis developed and those in whom it did not develop. The hepatitis was associated with more than one batch of a Swedish intravenous immunoglobulin, the immunoglobulin being derived from United States sources as well as from European plasma. Three previous brief reports in the literature have also associated non-A, non-B hepatitis with the intravenous infusion of various immunoglobulins. Biologic materials given to patients, including immunoglobulin, should, whenever possible, be prepared so as to ensure absence of viruses.