Whereas it is well known that idiopathic HCM can present in newborns and infants, little information is available on HT in this very young age group. We report a series of 17 infants with idiopathic HCM, including two neonates with rapidly progressive severe HF for whom HT was necessary. When HF manifests in a newborn/infant with idiopathic HCM and extreme cavity size reduction, the possibility of a rapidly progressive clinical course should be anticipated and HT may become the only available therapeutic solution.