In contrast to the high success rates for catheter ablation of focal ventricular tachycardia, radiofrequency ablation for ventricular tachycardia due to coronary artery disease has met with limited to variable success. In performing catheter ablation for ventricular tachycardia due to coronary disease, mapping techniques used to locate the isthmus of the reentrant circuit are crucial. Appropriate use of mapping techniques determines the success rate of the procedure. We classify different methods of mapping into indirect and direct. The indirect methods include analysis of the 12-lead electrocardiogram, endocardial pace-mapping, and analysis of electrograms recorded from different parts of the heart during sinus rhythm. The direct methods include activation sequence mapping and entrainment mapping. The direct methods are more important in evaluating ventricular tachycardia due to coronary disease. While using the technique of entrainment mapping, three criteria are important: a) entrainment with concealed fusion; b) post pacing interval within or less than 10 ms of tachycardia cycle length; c) stimulus-to-QRS interval should equal electrogram-to-QRS interval. A high success rate in terminating the tachycardia is seen if these criteria are met.