Multiple sclerosis is the most common cause of neurologic disability in young adults. Recent reports have suggested that Mitoxantrone might be a candidate for clinical trials in multiple sclerosis patients. The authors studied 20 patients with relapsing remitting multiple sclerosis to evaluate cardiac toxicity during a one-year follow-up period. Patients were divided into 2 groups: group A, mitoxantrone treated patients (cumulative dose of 96 mg/m2); group B, placebo patients. The clinical course of multiple sclerosis was assessed using the Expanded Disability Status Scale and the number of relapses during the follow-up. Each patient had an electrocardiogram and a spectral and color flow Doppler echocardiographic examination at enrollment, and 6 and 12 months later, to investigate cardiac toxicity. The mean exacerbation rate was reduced significantly in group A patients. No significant differences in the electrocardiograms or the echocardiographic parameters of systolic and diastolic function were noted between the two groups or in group A during the follow-up. Mitoxantrone treatment seems able to improve the clinical course of relapsing remitting multiple sclerosis patients. It does not show any cardiac toxicity in selected patients at this dosage.