Two monoclonal antibodies suitable for leukemia cell purging of remission bone marrow from patients with common acute lymphoblastic leukemia (common-ALL) are described. WM-21, reacting with the gp 100 common-ALL associated antigen (CALLA), and FMC-8, reactive with a p24 surface antigen, both bind to the majority of leukemic blast cells from cases of common ALL, and promote complement-mediated lysis of CALLA+ leukemias and cell lines. After initial dye exclusion studies to standardize antibody and rabbit complement concentrations and incubation times, an in vitro plating assay using CALLA+ p24+ cell lines was used to investigate the lytic ability of monoclonal antibody treatment. Incubation with WM-21, FMC-8, and complement produced up to 5 logs inhibition of growth in this system. Under similar conditions, no inhibition of in vitro growth of normal bone marrow myeloid progenitor cells was seen. These antibodies therefore appear to be useful therapeutic reagents for removing residual common ALL blast cells from bone marrow prior to autologous marrow transplantation.