The search for useful molecular markers in the diagnosis of AML and in the follow-up of minimal residual disease (MRD) has been the focus of many recent studies. Previous research showed that, while normal bone marrow cells lack expression of renin, myeloid blasts have been reported to do so. The aim was to study the expression of the renin gene by the use of real-time quantitative PCR (RQ-PCR) at diagnosis in acute myeloid leukemia patients (AML) and to assess its possible relevance in the prognosis and outcome of such patients. This study analysed 76 samples from patients with AML, with follow-up of positive patients. Thirty-one patients (41%) were positive for renin gene expression at diagnosis. All renin-positive patients at diagnosis showed no expression during complete remission (CR), but expression recurred in those experiencing relapse and persisted when the disease was refractory to treatment. Although the results suggest that the sub-group of renin-positive AML patients might have a worse outcome and a higher relapse rate (at 5 years, the projected rate of disease-free survival was 18.5 +/- 9.8% for renin-positive and 23.5 +/- 8.8% for renin-negative patients), no significant differences were found. It is believed that further studies should aim to validate whether such a difference exists, using a much larger and homogeneus group of patients.