Diabetes mellitus was assessed by investigating 8 type I diabetic patients, in good metabolic control and with congestive heart failure who were studied after 3 weeks of placebo and ibopamine (100 mg t.i.d.) treatment. Metabolic control and daily insulin dose did not change in any patient during the study. The insulin-mediated glucose uptake during the clamp studies showed no variation after placebo or ibopamine therapy. Total cholesterol, HDL-cholesterol and triglycerides concentrations remained unchanged. This study clearly suggests that ibopamine administered at a daily dose of 300 mg for 3 weeks presents a metabolic safety in type I diabetic patients.