A 1-year-old child weighing 8 kg with familial congenital junctional ectopic tachycardia that was difficult to treat with antiarrhythmic medications underwent successful cryoablation with preservation of atrioventricular (AV) nodal function. This report describes a strategy of cryoablation in conjunction with a 3-D mapping system and the use of atrial overdrive pacing during cryothermal application to assess AV nodal function.