Human Granulocyte Macrophage Colony-Stimulating Factor (hGM-CSF) is one of the hematopoietic growth factors which plays an important role in hematopoietic cell proliferation, differentiation of hemopoietic precursor cells. The hGM-CSF is more effective in treating the neutropenia caused by chemotherapy for cancer treatment. The recombinant hGM-CSF produced in genetically engineered Escherichia coli was approved for chemotherapy-induced neutropenia. In this work we compared the biological activity of rhGM-CSF which is produced in (NRCGEB) and Sandoz on the colonogenesis of HL-60 and U-937 cell lines. For assessing the biological activity of rhGM-CSF on proliferation of HL-60 , we performed NBT, Brdu , and MTT test and on U-937 cells, we also performed MTT test on U-937 cells. The cells cultured with different concentration of rhGM-CSF (0-400000 pgr/ml). RhGM-CSF showed stimulating effect in doses of 40 and 400 pg/ml but showed inhibitory effect in doses of 400-400,000 pg/ml. rhGM-CSF can shorten cell cycle times in dividing colony cells, and influence the differentiation of colony cells with a very rapid action on target cells. Sandoz rhGM-CSF can influence more than NRCGEB rhGM-CSF on the colonogenesis of HL-60 in doses of 40 and 400 pg/ml. Proliferation of U-937 cell line in serial dilutions of Sandoz is more than NRCGEB rhGM-CSF on MTT test, but Sandoz rhGM-CSF showed stimulating effect in doses 0, 4000 , 40 000 ,400 000 pg/ml in proliferation of HL-60. Results of MTT test on HL-60 differs with NBT and Brdu test.The obtained results are obtained from different sensitivity of these three techniques.