Reported experience with the transseptal approach to the left atrium for delivery of radiofrequency energy in the young patient is limited. To compare two approaches for radiofrequency ablation (RFA) in the left atrium we reviewed our experience from January 1, 1991, through February 1, 1999, in 154 procedures performed on 136 patients (mean age 12.2 years). The patients were grouped by either the retrograde aortic route (R, n = 30) or the transseptal atrial route (T, n = 106). No significant differences were found in age, weight, height, supraventricular tachycardia cycle length, or electrocardiograph characteristics (manifest vs concealed accessory pathway) between the two approaches. Comparison of the transseptal group to the retrograde aortic group revealed a significant difference in the number of catheters (mean = 4 R vs 3 T, p < 0.0001), total fluoroscopic time (71.3 min R vs 43.0 min T, p = 0.0007), diagnostic fluoroscopic time (40.2 min R vs 16.6 min T, p < 0.0001), ablation fluoroscopic time (44.7 min R vs 25.3 min T, p = 0.019), and procedure time (5.0 hours R vs 4.1 hours T, p < 0.0001). No significant difference was found in success rate, number of radiofrequency applications, or major complication rate. These data suggest that although outcomes and major complication rates are similar for the two groups, the use of fewer catheters and shorter fluoroscopic times warrant consideration of the transseptal atrial approach in young patients.