Nine patients with the acquired immunodeficiency syndrome (AIDS) were administered four doses of pooled transfer factor obtained from the lymphocytes of three healthy controls and three homosexuals with stable lymphadenopathy and serum antibody to the human immunodeficiency virus. Before receiving transfer factor, all patients exhibited anergy to skin test antigens. After four weeks of transfer factor therapy, six of seven patients tested had at least one skin test response. Lymphocyte blastogenic responses to phytohemagglutinin rose from a stimulation index of 6.77 ±1.31 before treatment to 19.77 ±6.24 after four weeks of transfer factor therapy. Smaller but significant increases were also seen in blastogenic responses to antigens. Improvements in immune responses diminished after administration of transfer factor was halted. Thus, administration of transfer factor to patients with AIDS resulted in partial immune reconstitution. Further studies are indicated to examine the clinical efficacy of this immune response modifier in the treatment of AIDS.