As a result of blunt chest trauma a patient developed a large ventricular septal defect (VSD). After surgical closure of the defect a grade 2/6 systolic murmur persisted. One year later findings were the same and left ventriculogram revealed a small residual VSD. Two years after the operation the systolic murmur had disappeared. We postulate that gradual endothelialization and possibly small thrombi (formed around and over the Dacron patch graft) caused the defect to close. This case serves to illustrate some of the Dacron patch graft) caused the defect to close. This case serves to illustrate some of the complexities in the diagnosis and management of an acquired VSD. To our knowledge this is the first reported spontaneous closure of a VSD occurring after incomplete surgical repair.