Abstract: The present invention relates to the use of a non-lethal preparative regimen for the treatment of a patient with human immunodeficiency virus (HIV) disease. In a clinical trial, an HIV-positive patient was conditioned by non-lethal doses of irradiation and a chemotherapeutic drug prior to receiving donor bone marrow cells from a baboon. While long-term engraftment of donor cells was not observed, the non-lethal preparative conditioning regimen was able to reduce the viral burden and improved the clinical outcome. Such method is useful for treatment of patients with advanced acquired immunodeficiency syndrome (AIDS).