We report an asymptomatic 18-month-old boy who underwent surgical resection of the discrete subaortic stenosis. Histopathologic examination of the muscle demonstrated diffuse lymphocytic infiltration of the myocardium. Polymerase chain reaction analysis of blood demonstrated parvovirus. This report highlights that asymptomatic myocarditis may be more prevalent than we realise, and that involvement of the myocardium by parvovirus may be entirely asymptomatic.