Leukocytes and their subpopulation have been long implicated in the progression of the syndrome of heart failure (HF), especially heart infiltration cells. Previous reports have suggested that they can predict worse outcome in patients with HF, and can also affect the function of other cells and myocardial extracellular matrix remodeling process. However, the lymphocyte-to-monocyte ratio (LMR) and its possible value as prognostic marker have not been evaluated.A total of 390 patients with acute HF were recruited and followed for 6 months. Their total blood count with leukocyte differential was obtained. Two groups were formed according to the endpoints of HF death and optimal cut-off value of LMR, and were compared. A multivariate Cox-regression model was used to establish the prognostic value with the endpoints of HF and all-cause mortality. Median age of the patients was 78 years and 48.5% of them were men. No major difference was observed between the clinical characteristics of the two groups. Patients who died of HF had significantly higher values of B-type natriuretic peptide and lower values of LMR. Leukocyte and monocyte counts revealed a multivariate-adjusted risk for both endpoints, whereas relative lymphocyte counts had only significant value for all-cause mortality. The multivariate-adjusted hazard ratios for the 6-month HF and all-cause mortality in patients with LMR values < 2.0 were, respectively, 2.28 (95% CI: 1.25-4.15) and 2.39 (95% CI: 1.39-4.10).Our results show that, upon discharge from hospital after an episode of acute HF, a lower value of LMR is independently associated with a higher risk of mortality within 6 months.