Permanent junctional reciprocating tachycardia (PJRT) is a rare form of supraventricular tachycardia that primarily affects infants and young children. PJRT is a type of reentrant tachycardia, often involving an accessory pathway called the “Kent bundle.” This accessory pathway enables electrical impulses to bypass the normal electrical conduction system, leading to a rapid and abnormal heart rhythm. Common symptoms of PJRT include palpitations, fatigue, and shortness of breath, with infants frequently experiencing feeding difficulties. PJRT management usually consists of antiarrhythmic medications, such as β-blockers or calcium channel blockers, to control the heart rate. However, in cases where medications are ineffective in suppressing the arrhythmia, known as drug-resistant PJRT, alternative treatment options must be considered. PJRT is characterized by a re-entry pathway involving the atrioventricular node and an accessory pathway, resulting in incessant and rapid heart rates. In instances where medications are unsuccessful in controlling the arrhythmia, ablation utilizing 3D mapping technology offers a promising therapeutic option. This article examines a case where an infant with drug-resistant PJRT for 1 year was successfully treated with ablation, facilitated by the use of a 3D mapping system. (Iranian Heart Journal 2024; 25(3): 80-84)