Atrial tachycardias (ATs) may be divided into focal and reentrant forms. In recent years, great prngress achieved in catheter ablation of ATs and the success rate of catheter ablatiou has improved dramatically in both focal ATs and reentrant ATs.Focal ATs tend to originate in characteristic locations associated with anatomic structures, such as the erista terminalis,the interatrial septum,the atrioventricular annulus,the coronary sinus,the atrial appendages,the ostial portion of the pulmonary veins. In recent years, successful catheter ablation of focal AT from the nou-coronary aortic sinus, from the mitral annulus-aorta junction, or from the atrial ap-pendages has been reported. Catheter mapping and ablation in the non-coronary aortic sinus should be attempted in patients with narrow P waves on surface ECG and the earliest atrial activation located at the His bundle region. For the cases who had a failed ablation or recur-rence after ablation in the non-coronary aortic sinus,mapping and ablation in the mitral annulus-aorta junction should be considered.Catheter ablation of typical atrial flutter (AFL) has a very high success rate,approximately 100% in some centers. For few difficult cases,several measures can be employed to increase the likelihood of success. Firstly and most importantly,the mechanism of typical AFL other than other ATs should be revaluated and reconfirmed. Other measures include using three-dimensional cardiac electroanatomical mapping system to map the cavotricuspid isthmus (CTI) carefully, using large-curve catheters and/or long guiding sheaths to ensure cath-eter contact across the entire CTI,and employing a large-tip or cooled-tip catheter instead of standard 4 mm-tip ablation catheter.Reentrant ATs usually occur in patients with dilated, severely scarred right or left atria, including previous right or left atriotomy, any form of structural heart disease, or following catheter or surgical ablation of atrial fibrillation. Some reentrant ATs patients present with a large scarred right or left atrium without any other form of structural heart disease, were classified it as "idiopathic arrhythmogen-ic atrial myopathy" by some experts. The earlier experience in mapping and ablation of reentrant ATs came mainly from mapping and ablation of ATs in patients with sugical treatment of congenital heart disease,so the ATs were called "incisional reentrant ATs". In the past decade, the success rate for catheter ablation of reentrant ATs after surgery has improved significantly by combination of electroana-tomical scarred substrate mapping and entrainment mapping. It is noted that the "incisional reentrant ATs" often have multiple reentrant circuits and multiple ATs or coexist with typical AFL, and more than one linear lesions from scar to scar, or scar to anatomical obstacle, or between reentrant isthmuses are needed in most cases.The reentrant ATs after catheter ablation of atrial fibrillation have increased dramatically in recent years, which belong to "iatro-genic reentrant ATs". Different atrial fibrillation ablation approaches have different incidence of reentrant ATs, a few in patients with segmental isolation of the pulmonary vein ostia, more often in patients with circumferential pulmonary vein ablation and most often in pa-tients with stepped ablation of chronic atrial fibrillation (combination of pulmonary vein isolation, linear ablation and ablation of the complex fractionated atrial electrograms). In some cases, mapping and ablation of these reentrant ATs are very difficult.