A patient with hemophilia A developed T-cell deficiency characterized by infection with several opportunistic pathogens. Immunologic investigation showed cutaneous anergy, lymphocyte unresponsiveness to mitogens and antigens, an abnormal ratio of T-helper and T-suppressor cells with absolute lymphopenia and elevated IgA. The clinical and immunologic characteristics of this patient fit the recently described syndrome of opportunistic infections or Kaposi's sarcoma in patients with acquired T-cell deficiency; however, this patient does not have any of the associated underlying risk factors such as homosexuality, intravenous drug or amyl nitrite use, or positive serologic tests for syphilis. We conclude that the patient's acquired T-cell deficiency can be explained by exposure to a virus or other transmissible agent during factor VIII transfusions.