Catheter-based radiofrequency ablation with pulmonary vein (PV) isolation has emerged as an effective therapy for patients with symptomatic atrial fibrillation. Real-time intracardiac echocardiography with two-dimensional and Doppler colour flow imaging can facilitate left heart ablation procedures. It allows identification of anatomic structures and potential anatomic variations. It has a critical rote for guiding transseptal catheterization, assisting placement of mapping and ablation catheters, and allows for titration of energy delivery. More importantly, it allows identification and potential reduction of procedural complications including damage to intracardiac structures, left atrial thrombus formation, PV stenosis, and pericardial effusion during left heart ablation.