Muscular ventricular septal defects (MVSDs) account for approximately 20% of all congenital ventricular septal defects. Large defects in infants result in early heart failure, failure to thrive and pulmonary hypertension. Although percutaneous closure of MVSDs has been employed safely and effectively in children, adolescents and adults, its application in the small infant (weight <6 kg) carries a higher risk for complications including arrhythmias, hemodynamic compromise, cardiac perforation, tamponade and death. Perventricular closure of such defects, introduced by Amin and coworkers in the late 1990s, has become an attractive treatment modality for these small and high-risk patients. Experience worldwide has shown that the procedure is feasible, reproducible, safe and effective. In this article, the authors review the indications, the step-by-step technique and the results of perventricular closure of MVSDs using the AMPLATZER mVSD device (AGA Medical, MN, USA).