Background: Chronic Myeloid Leukaemia (CML). It is a type of myeloproliferative disease associated with a characteristic chromosomal translocation t (9;22)(q34;q11). P-Stat3Tyr705 is activated in a bcr-abl independent manner by the cytokine milieu. Experimental evidence indicates that Stat3 plays a very crucial role in hematopoiesis. Additional research, however, suggested a more complex role for Stat3 in neutrophil regulation. Attractive to speculate that inhibition of p-Stat3Tyr705 activity would lead to drug sensitization and cell death in CML cells. Taken together, this study aims to assess the level of p-Stat3Tyr705 expression cell populations in CML patients and in normal controls involving each of myeloid and lymphoid cell populations. Methods: The study included 50 CML patients and 20 normal healthy controls. P-Stat3Tyr705 expression was assessed in each of myeloid and lymphoid cells as indicated by plotting analysis of the samples by flowcytometric analysis and gating these cell populations on the forward and side scatter.  Results: This work revealed increase in the level of expression of p-Stat3Tyr705 in CML patients than in normal healthy controls regarding myeloid cells with no difference found regarding lymphoid cell population. Also it was encountered that the expression of p-Stat3Tyr705 is higher on myeloid cells than in lymphoid cells in CML patients. A difference which is not found in healthy controls. No correlation between p-Stat3Tyr705 and bcr-abl quantitation was detected. Conclusion: The increase in the p-Stat3Tyr705 expression over the myeloid cells is a part of the pathological events of the disease process and not found in the normal physiological conditions. The myeloid cells can be considered the pathologic target of p-Stat3Tyr705 over expression in the disease process.