The instant invention relates to transseptal access systems and methods for accessing the left atrium from the right atrium by crossing the interatrial septum. In particular, the instant invention is directed toward medical devices used with catheter assemblies in cardiology procedures that require transseptal puncture(s). The puncture assemblies have a moveable puncture device within a dilator. The puncture device is biased in a retracted position. The position of the puncture assembly is precisely locatable. The puncture assembly is preferably flexible along the majority of its length, and, therefore, can be used with any catheter assembly of any predetermined shape. The puncture device is adjustable from a position within the dilator to a position extending beyond the end of the dilator when necessary for use in transseptal procedures.
