Catheter ablation has come to play an important therapeutic role in the management of some patients with ventricular arrhythmias. An important advance in catheter ablation of ventricular tachycardia (VT) has been the development of three-dimensional catheter-based mapping systems, which permit identification of the tachycardia circuit and facilitate a strategy for catheter ablation. As a result, patients who suffer from "focal" forms of VT have been identified. This can have implications with respect to underlying arrhythmia mechanism, patient prognosis, and therapeutic strategies. The article reviews some insights learned from catheter ablation of focal forms of VT.