It has been widely assumed that anti-HLA-DR antibodies react with pluripotent stem cells and cannot be used in bone marrow purging. We report a case of non-Hodgkin's lymphoma in which an anti-HLA-DR antibody (AB4) was used for immunomagnetic purging and the subsequent autologous bone marrow transplantation resulted in rapid marrow engraftment with no serious complications. The results indicate that the AB4 antibody, which binds to an antigen encoded by the B3 gene of the DR region, can be safely used in the clinic in the purging of bone marrow from patients with AB4-positive tumors (non-T-cell acute lymphocytic leukemia, non-Hodgkin's lymphoma, and some cases of acute myelogenous leukemia.