Mapping and ablation of post–atrial fibrillation (AF) atrial tachycardia (AT) are challenging electrophysiologic procedures. These tachycardias may be caused by multiple mechanisms and may arise from the left or right atrium, or the coronary sinus. The precise mechanism must be defined before ablation because the procedural end point depends on the correct diagnosis. Postablation ATs can be successfully ablated in approximately 90% of patients. Many patients experience recurrence despite rigorous procedural end points. Efforts should focus on decreasing the incidence of AT after AF ablation and identifying patients who require linear ablation during a procedure for persistent AF.