Objective To study the expression of human telomerase reverse transcriptase (hTERT) and P16 protein and their relation with telomerase activity in the carcinogenesis of acute leukemia. Methods Telomerase activity and hTERTmRNA were detected in 40 patients with acute leukemia and 20 normal controls by TRAP and RT-PCR, respectively; P16 protein was examined by immunocytochemical method. Results The positive rates of telomerase activity and hTERTmRNA were 75% and 80% in 40 cases of acute leukemia, respectively, whereas neither hTERTmRNA nor telomerase activity was detected in normal controls. There was a significant correlation between the expression of hTERTmRNA and telomerase activity (r= 0.65, P