Transcatheter aortic valve implantation has been shown to be an effective and reproducible therapy for severe aortic valve stenosis. Device performance and short-term outcomes of well-deployed prostheses have been extensively investigated and discussed; however, these endpoints have not yet been reported in cases characterized by suboptimal expansion. We describe a case of CoreValve self-expanding prosthesis underexpansion, reporting data on prosthesis performance and short-term clinical outcome.