Intracardiac echocardiography, defined as ultrasonographic navigation and visualization within large blood-filled cavities or vessels of the cardiovascular system, has recently undergone refinement as a clinical tool through technologic advances in transducer miniaturization. Intra-cardiac ultrasound catheters image at lower frequencies than current conventional intravascular ultrasound catheters used for intracoronary imaging. The lower imaging frequency enables greater tissue penetration, permitting whole-heart evaluation Newer devices are steerable, nave variable imaging frequency (5.5 to 10 MHz), and full Doppler capability (pulsed, continuous wave, and tissue Doppler). These advances have made intracardiac high-resolution imaging as well as hemodynamic assessment possible. A historical perspective, current capabilities and limitations, and potential clinical and research applications of this new imaging technique are discussed. from a right-sided catheter position.