The key to a successful catheterization of the left heart chambers is the safe transseptal puncture. Intracardiac echocardiography (ICE) is an attractive tool used in cardiac catheterization and electrophysiology labs to provide detailed images thatcan facilitate transseptal puncture. ICE permits a direct visualization of the endocardium and precisely locates the needle and the sheath against the interatrial septum. Two different ICE catheters are available: a phased array and a mechanical transducer, both being currently used in clinical practice. This paper describes the technique used for guiding transseptal puncture with ICE. Due to its advantages, ICE has currently become an important tool used to maximize the safety of the transseptal puncture and increase efficacy of interventional cardiology procedures.