We present the case of 23-year-old woman with good living conditions, one year history of ventricular arrhythmia and 6 months history of decreased exercise tolerance, who was found to have dilated cardiomyopathy after aborted sudden death. Endomyocardial biopsy did not show specific findings. Within 3 months she developed profound bradycardia requiring pacemaker implantation and refractory heart failure, treated with heart transplantation. Intense eosinophilic myocarditis was found in the explanted heart. Retrospective analysis of the patient's blood count revealed mild eosinophilia (eosinophil count: 0.86 x 109/l) on one examination only. Following heart transplantation the patient had persistent eisinophilia (eosinophil count: 0.62 x 109/l). Although there was no proven parasitic infestation, based on positive family history of Enterobius vermicularis infestation she was treated with broad-spectrum antiparasitic agent: albendazole and her eosinophil count returned to normal values. This case shows that active eosinophilic myocarditis may present clinically as progressive dilated cardiomyopathy with severe involvement of conduction system. Massive myocardial tissue eosinophilia occurred in the setting of mild and transient blood eosinophilia. Favourable outcome following antiparasitic treatment suggests a potential parasitic infestation as a cause of the disease.