**1. Introduction**

The use of bioprosthetic valves in aortic valve replacement (AVR) has been increasing, even in younger patients [1]. In the meantime, the indication of transcatheter aortic valve replacement (TAVR) has been expanding as well. Since reoperation for degenerated prosthetic valve carries a high risk, a valve-in-valve TAVR has become an attractive alternative treatment. The most recent guidelines stated that valve-in-valve TAVR is recommended as class IIa indication for "severely symptomatic patients with bioprosthetic aortic valve stenosis judged by the heart team to be at high or prohibitive risk of reoperation, and in whom improvement in hemodynamics is anticipated" [2]. However, technical challenges exist in valve-in-valve TAVR. In this chapter, we discuss the current perspective of valve-in-valve TAVR and its associated risks and benefits.
