This paper describes the development of a semiautomated procedure for autologous bone marrow processing, prior to ex vivo manipulation and/or cryopreservation. This procedure was employed with a pediatric bowl (125 ml Latham bowl) and the automated DuPont Stericell processor. We have obtained a mononuclear cell recovery of 85% and a hemopoietic progenitor cell recovery of 81% (CFU-GM; BFU-E), with a red cell removal of 84%. We believe that a reliable and standardized bone marrow processing procedure is the basic necessity for a bone marrow transplantation program.