Chronic myelogenous leukemia is a hematopoietic stem cell tumor that accounts for 15% - 20% of all leukemia cases. Diagnosis of the disease is by physical exam, complete blood counts, peripheral blood smear, bone marrow aspiration, cytochemistry, imaging and genetic analysis. The final diagnosis of CML is performed by finding the genetic translocation, t(9;22), the Philadelphia Chromosome (Ph) which form a BCR-ABL fusion oncogen. A new biological treatment that inhibits this chromosome, BCR-ABL tyrosine kinase inhibitors (TKIs), alters the outcome of CML patients from one with shortened life expectancy to a long-term survival. New generation of TKIs were introduced in the last few years, including nilotinib, dasatinib, bosutinib, and ponatinib; all which have a better and faster responses. Many clinical trials are still ongoing and we are eagerly awaiting results. Epidemiology, the Philadelphia chromosome, clinical phases, monitoring techniques, and treatments (including TKIs, chemotherapy, interferon alpha, and stem cell transplantation) of CML are reviewed in my thesis.