Growth kinetics of bone marrow stromal layers from normal, AML, ALL and CML patients was studied. Significantly reduced time for confluency was observed in AML patients in complete remission, in CML patients in chronic phase, or CML patients after allogenic bone marrow transplantation. The functional capacity of these stromal layers did not differ: they all bound similar amounts of blast colony forming cells (BL-CFC) from normal bone marrow. The stromal layers from bone marrow transplanted patients varied in their BL-CFC binding capacity: two CML patients (10.5 and 49 months after transplantation) showed normal values, while two ALL patients (1.5 and 3 months, respectively, after transplantation) as well as one patient transplanted for CML (19.5 months after transplantation) showed significantly reduced BL-CFC binding capacity.