A 36-year-old male with mild Ebstein's anomaly developed severe right-sided heart failure, following a 5-year-long course of hypereosinophilic syndrome. No regular followups had been done, during the years of antineoplastic therapy. A year after being cured from the hypereosinophilic syndrome, the patient developed right-sided heart failure symptoms and was found to have excessive fibrosis of the right ventricular endocardium and free tricuspid regurgitation. The findings were compatible with substantial scarring of the endocardium caused by the hypereosinophilic syndrome. Over a few years, the patient deteriorated significantly and was finally offered a heart transplant. Examination of the explanted heart revealed severe fibrosis of the right ventricle and almost complete sparing of the left.