Abstract A partially purified human urinary colony-stimulating factor (pp-CSF), with a specific activity of 1.0 × 10 6 U/mg protein, was purified by using a stepwise DEAE-cellulose anion exchange chromatography and a molecular sieve high performance liquid chromatography (TSK gel G3000SW) sequentially. Production of three kinds of monokines by human peripheral blood monocytes was tested in vitro, which contained granulocytic colony-stimulating activity (G-CSA), interleukin 1 (IL-1) and intefferon α(IFN-α). Human peripheral blood mononuclear cells were separated by Ficoll-Hypaque density gradient centrifugation, and monocytes were obtained by adherence to dishes. Although pp-CSF stimulated monocytes to produce G-CSA in vitro, it failed to stimulate the IL-1 or IFN-α production. The discrepancy between production or release of these three kinds of monokines by human monocytes stimulated with pp-CSF suggests that pp-CSF preferentially stimulates human monocytes to produce G-CSA. To test the effects of pp-CSF on human monocytes in vivo, we performed i.v. infusions of pp-CSF to four volunteers, and we then took peripheral blood monocytes. Compared to before the infusion of pp-CSF, G-CSA production by monocytes was enhanced, while production of IL-1 and IFN-α was not enhanced after the infusion of pp-CSF. These results suggest that pp-CSF stimulates monocytes to produce G-CSA but not to produce IL-1 nor IFN-α.