The purpose of this study was to investigate whether levels of hTERT mRNA, as determined by real-time RT-PCR, are associated with prognosis and clinical course in AML patients. Fifty-four bone marrow specimens from 21 patients diagnosed with de-novo AML were included. The level of hTERT mRNA was measured with the Telo TAGGG hTERT Quantification Kit (Roche Diagnostics, Mannheim, Germany), using a LightCycler Instrument (Roche Diagnostics). The level of hTERT mRNA was determined as the relative ratio (RR), which was calculated by dividing the level of hTERT mRNA by the level of the porphobilinogen deaminase (PBGD) housekeeping gene in the same samples [1,000 × (hTERT/PBGD)]. The expression rates of hTERT mRNA were significantly higher at diagnosis (73%) and during relapse (80%) than during remission (27%) (P < 0.05). The median RR for diagnosis or relapse was significantly higher than that for patients in remission (P < 0.05). hTERT mRNA expression was not correlated with CD34 expression, blast counts, white blood cell counts, or chromosomal abnormality (P > 0.05). Two patients who showed hTERT mRNA expression during remission (RR 3.14 and 7.15, respectively) relapsed after 1 month. Among seven patients with high hTERT mRNA levels (RR > 9.51), 4 failed to achieve complete remission (CR), whereas 4 of 5 patients without hTERT mRNA expression at diagnosis or during relapse achieved CR (P > 0.05). Patients showing a trend of increasing hTERT mRNA levels failed to reach a second CR after relapse, while those with a trend toward decreasing hTERT mRNA did achieve CR. Among eight samples showing hTERT mRNA expression in remission (RR > 0), 5 were obtained from patients who had received GCSF within 14 days. The expression rate and level of hTERT mRNA during remission were significantly higher in patients who had previously received GSCF (56%, RR = 0.15) than in other patients (15%, RR = 0) (P < 0.05). Serial and quantitative analysis of hTERT mRNA may be a useful marker for prediction of prognosis and monitoring in AML patients. Am. J. Hematol. 79:267–273, 2005.© 2005 Wiley-Liss, Inc.