The substitution of digoxin with ibopamine, a new inotropic and vasodilating agent, was evaluated in a multicenter study in 58 patients with mild-to-moderate congestive heart failure, stabilized on diuretics, and digoxin therapy. The study was a parallel, double-blind, randomized trial of four weeks duration in which half of the group continued the pre-study medication (diuretics and digoxin) and half of the group was treated with diuretics and ibopamine (100 mg, three times a day). At baseline evaluation, the two groups were similar for age, sex, underlying cardiac disease, duration of congestive heart failure, symptom score, cardiothoracic ratio, echocardiographic parameters of left ventricular function and exercise tolerance as measured by bicycle ergometry. After four weeks, no clinical deterioration was found in the patients treated with ibopamine in any measured parameter. There were two deaths during the study: a sudden death and one following an acute myocardial infarction. Both patients were on digoxin. This study suggests that in patients with mild-to-moderate congestive heart failure, ibopamine therapy may effectively and safely substitute digoxin therapy for up to four weeks, representing an option for patients requiring inotropic support but are at risk for potential digoxin toxicity.