Digoxin therapy has long been used to treat heart failure; however, its effectiveness was not completely known until recently. Results of the Digitalis Investigation Group trial showed that adding digoxin to standard heart failure therapy had no effect on mortality. However, adding digoxin decreased hospitalizations related to heart failure and improved symptoms in patients treated for heart failure. Reanalyses of the trial's findings have raised new questions about the role of digoxin in heart failure treatment. These new analyses showed that low serum digoxin concentrations used in patients with more severe disease offered the most benefit. Digoxin use in women was associated with increased mortality risk. This finding should be interpreted with caution, however, because it was based on retrospective data, and the cause of this phenomenon has not been fully elucidated. Prospective clinical trials are needed to determine the serum digoxin concentration that is associated with the most clinical benefit and to determine the role of digoxin therapy for women. Digoxin generally does not have a role in the treatment of diastolic heart failure and is not a first-line therapy for managing atrial fibrillation in patients with heart failure.