The interactions between granulocyte colony-stimulating factor (G-CSF) and dextran sulfate (DS) with different chain lengths and sulfate contents were studied by capillary zone electrophoresis. It was found that DS with a molecular mass of 500 kDa (DS500) could bind to G-CSF and the binding constant and binding sites were determined using Scatchard plot to be 1.17 x 10(6) M-1 and 8, respectively. DS with a molecular mass of 40 kDa also had the affinity to G-CSF and the binding constant and binding sties were 1.01 x 10(6) M-1 and 8, respectively. However, DS with a molecular mass of 8 kDa and the non-sulfated saccharide, dextran, had no affinity to G-CSF The results indicate that the interactions between G-CSIF and DS are dependent on the chain lengths and sulfate contents of the saccharides. In addition, the effects of G-CSF-binding DS on a G-CSF-dependent leukemia cell line were investigated using biological methods. Results show that DS500 plus G-CSF has potential therapeutic effect on cancers because their combination could inhibit the growth and induce the differentiation of the leukemia cells.