434 electrocardiograms were performed on 62 patients with uncomplicated forms of schistosomiasis mansoni treated with hycanthone intramusculary in the dose of 2,5 mg/kg. Registering roas made before, during and after treatment. Although electrocardiographic changes were recorded in 67,74% of patients, they were so slight that the authors suggest the study of using the drug on cases of cardiovascular disease.