Background: Chronic myeloid leukemia (CML) is a myeloproliferative illness marked by a reciprocal translocation between chromosomes 9 and 22 [t (9;22) (q34; q11)], forming the Philadelphia chromosome and bringing together the Breakpoint Cluster Region (BCR) and Abelson (ABL1) genes. The protein expressed by this fusion gene is a dysregulated tyrosine kinase that causes alterations in cell proliferation, DNA repair, differentiation, and cell cycle by phosphorylating many downstream proteins. Objectives: To assess PTCH1 gene expression and response of adult patients with chronic myeloid leukemia to imatinib treatment. Patients and Methods: This is a prospective case-control study that included 55 subjects; 45 patients with chronic phase chronic myeloid leukemia and 10 healthy age and sex-matched controls. The control group presented from the same geographic origin of the patients in the study group. The study was done between June 2015 and July 2017 at the hematology clinic, Ain Shams University Hospital. Results: PTCH1 gene was more in cases than control with a statistical significance (P-value=0.024). On following up our cases after 6 months treatment with imatinib, patients with desired response to imatinib treatment had a mean of PTCH1 gene expression of 2.41, compared to 3.58 in patients who did not achieve desired response with a statistical significance with p-value = 0.017. Incidence of imatinib failure after 6 months of treatment in patients with high PTCH1 expression is 27.8 % while in those with low expression is 44.4 %. Conclusion: The study demonstrates that level of PTCH 1 did not affect imatinib response. Therefore, PTCH1 is not a valid biomarker for imatinib resistance in CML patients.