The present study is a therapeutic trial of phase I, based on the principle of passive immunotherapy in acquired immunodeficiency syndrome (AIDS). Eighteen patients with full blown AIDS (stage IV C2 of CDC) were subdivided into two groups: nine receiving every two weeks 300 ml of plasma collected from HIV-1 seropositive symptomless (stage II or III of CDC) individuals, and nine (control group) receiving 300 ml of seronegative plasma at the same rythm and for the same period. Each patient received seven transfusions. Clinical and biological results during the transfusional and post-transfusional periods are reported.