A new method for an assay of human granulocyte colony-stimulating factor (hG-CSF) has been developed using human promyelocytic HL-60 cells. The proliferation of HL-60 cells had been suppressed by the addition of dimethyl sulfoxide (DMSO) or retinoic acid (RA). These differentiating agent-treated HL-60 cells exhibited an increase in their number in response to recombinant hG-CSF (rhG-CSF). Neither dibutyl-cAMP nor interferon-gamma (IFN-gamma)-treated HL-60 cells, however, showed an increase in their number in response to rhG-CSF. The proliferation rate of DMSO-pretreated HL-60 cells was linearly increased from 0.3 to 10 ng/ml of rhG-CSF. L-Value of HL-60 cells assay was 0.027 +/- 0.012. The activities of non-glycosylated rhG-CSF produced by Escherichia coli and glycosylated rhG-CSF produced by chinese hamster ovary (CHO) cells were compared using DMSO-treated HL-60 cells; no significant difference between them. DMSO-treated HL-60 cells also responded to interleukin-3 (IL-3) and granulocyte-macrophage colony-stimulating factor (GM-CSF), but did not respond to erythropoietin or macrophage colony-stimulating factor, suggesting that the responsiveness of these cells to growth factor is restricted to myelogenic cytokines. In conclusion, DMSO- or RA-treated HL-60 cells are useful for the measurement of bioactivity of hG-CSF.