The telomerase activity of various hematologic disorders, including malignant and non-malignant ones is discussed in this paper. In total of 137 cases, each positivity of telomerase activity was MDS = 17/51, overt leukemia from MDS = 6/15, AML = 17/21, ALL = 4/6, CML-CP (chronic phase) = 0/10, CML-BC (blastic crisis) = 4/4, MPD (myeloproliferative disease)-BC = 3/3, CLL = 1/10, MM (multiple myeloma) = 0/6, aplastic anemia = 3/5, essential thrombocytosis = 0/3, and polycythemia vera = 1/3. The MPD-BC showed very high level of telomerase activity as well as CML-BC cases. From the analysis for 18 cases of AML and/or malignant lymphoma patients, significant results showed that the expression of cyclin D/E was not related to telomerase activity in these hematologic disease, as was not the case with breast cancer which was reported formerly.