Eight patients with hematological malignancies were treated with autologous blood stem cell transplantation (ABSCT). Hemopoietic precursor cells were mobilized into the peripheral blood (PB) by chemotherapeutic induction of transient myelosuppression followed by an overshooting of blood stem cell concentration. PB CFU-GM showed a 15-20 fold increase on days 15-20 after chemotherapy. Peripheral blood stem cells were collected by 5-8 continuous flow leukaphereses using a Fenwall CS 3000 blood cell separator when platelet and WBC count was rising rapidly (platelet greater than 50 x 10e9/L and WBC greater than 1 x 10e9/L). Mean CFU-GM collected per run by leukapheresis were 10.85 x 10e4/Kg (procedure 3), 10.03 x 10e4/Kg (modified procedure 1). Mononuclear cell suspension in 10% DMSO was frozen at controlled rate freezer (-1 degree C to -4 degrees C) and stored in the liquid phase of nitrogen. After thawing CFU-GM recoveries ranged from 13.8% to 81.5%; 55-70% of recovered cells excluded trypan blue dye.