Seventy patients with left atrioventricular accessory pathways and paroxysmal supraventricular tachycardia (PSVT) underwent radiofrequency catheter ablation (RFCA). The success rate was 94.3%. Among these patients, 26 had manifest preexcitation syndrome, and 44 had concealed preexcitation. Eighteen patients with concealed preexcitation underwent coronary sinus (CS) pacing, and delta wave appeared in 15. The keys to successful RFCA were correct positioning of the radiofrequency (RF) catheter tip, A/V amplitude ratio, AV interval (in sinus rhythm) and VA interval (during SVT or ventricular pacing). After 1-14 months of follow-up, two patients had supraventricular tachycardia (SVT) recurrence.