Background-The independent prognostic impact of diabetes mellitus (DM) and prediabetes mellitus (pre-DM) on survival outcomes in patients with chronic heart failure has been investigated in observational registries and randomized, clinical trials, but the results have been often inconclusive or conflicting. We examined the independent prognostic impact of DM and pre-DM on survival outcomes in the GISSI-HF (Gruppo Italiano per lo Studio della Sopravvivenza nella Insufficienza Cardiaca-Heart Failure) trial. Methods and Results-We assessed the risk of all-cause death and the composite of all-cause death or cardiovascular hospitalization over a median follow-up period of 3.9 years among the 6935 chronic heart failure participants of the GISSI-H...