In the present study, we used telomeric repeat amplification protocol assay (TRAP) and an internal telomerase assay standard to detect and quantitate telomerase activity in blood samples obtained from normal (control) subjects and acute leukemia patients. Telomerase activity was analyzed in 25 acute myeloid leukemia (AML) patients, and 25 acute lymphoblastic leukemia (ALL) patients and ranged from 1.7-171.3 RTA (mean 42.64±57.65) and 2.1-149 RTA (mean 40.73±39.55) respectively relative to the internal standard. Compared to the age-matched normal levels of telomerase activity in the peripheral blood cells, we determined that 21/25 (84%) of AML patients and 23/25 (92%) of ALL patients had heterogeneously elevated telomerase activity. Acute leukemia patients with high/moderate telomerase activity (AML: n= 12; ALL: n= 16) showed high leucocytic counts and more frequent extramedullary involvement during the disease. In AML, the level of telomerase activity was also associated with French-American-British (F AB) subtypes; patients with AML-M3 had normal to low telomerase activity.