Infections NFECTIONS with organisms of the genusPseudomonashave become a serious nosocomial problem.1These bacteria are frequently resistant to antimicrobial drugs. The treatment of these infections with commercial pooled γ-globulin (Cohn fraction II) has had, at best, limited success. In this report of a case, evidence is presented which suggests that plasma from a patient convalescing from aPseudomonasinfection may constitute effective therapy. The possible basis for the efficacy of such therapy is discussed. Report of Case A 5-year-old Caucasian boy was admitted to the Hospital of the University of Pennsylvania for the first time on Oct 29, 1963 with a two day history of vomiting, shaking chills, and fever. The patient had had aplastic anemia of unknown etiology for the previous six months. He had been treated for the past five months with testosterone propionate and prednisone. On this hormonal therapy the patient had shown