The use of a panel of monoclonal antibodies and anti-mouse immunoglobulin-coated microspheres is described for the depletion of leukaemic blasts from bone marrow. Marrow treated in this way rapidly reconstitutes haemopoietic function after high-dose consolidation chemoradiotherapy. The recovery of cells from bone marrow is similar but not identical to results obtained on removal of neuroblasts from marrow to be used for autologous transplant. This is probably a reflection of the cross-reactivity of 'anti-leukaemic' antibodies with a variety of haemopoietic progenitor cells. The study described here demonstrates the feasibility of using this method to purge leukaemic cells from bone marrow. A much larger randomised study between patients receiving either purged or non-purged bone marrow would be necessary to validate the need to remove small numbers of tumour cells from bone marrow.