Background We questioned whether the empirical four pulmonary vein (PV) isolation (4PVI) is necessary in patients with paroxysmal atrial fibrillation (PAF) clearly triggered from certain arrhythmogenic pulmonary veins (PVs). We hypothesized that selective or ipsilateral isolation of PV triggering AF (SPVI) is enough for this subgroup of PAF. Methods and Results We compared SPVI and 4PVI in 77 patients (Male 80.5%, mean age 53.0짹13.4 years) with PAF who underwent Lasso catheter guided catheter ablation. For SPVI (n=42), AF triggering PVs were identified by spontaneous or post-cardioversion immediate recurrence of AF. For SPVI, only AF triggereing PVs (1.5짹0.6 per patient) or ipsilateral PV antrum were electrically isolated. For 4PVI (n=35), each PV ostium was electrically isolated without further linear ablation. Results: 1. AF recurrence after 2 months of ablation was 26.2% in SPVI group and 22.9% in 4PVI group, respectively (p=NS). The total number of RF energy delivery was lower in SPVI than in 4PVI (51.0짹16.4 vs 127.2짹60.3, p<0.01), and the total procedure time (187짹79 min vs 326짹108 min, p<0.01) was shorter in SPVI than in 4PVI. 2. Among 11 recurrent patients in SPVI group, redo-ablation was performed in 9 patients. 55.6% (5/9) of recurrent arrhythmogenic foci showed reconnected PV potential (PVP) at the previously ablated PVs and 33.3% (3/9) were triggered from ipsilateral not-ablated PVs. 3. All 8 recurred patients in 4PVI group underwent redo-ablation, and all of them showed reconnected PVPs. We eliminated all PVPs and added cavotricuspid isthmus block in 3 patients, linear ablaiton in one, and focal ablation in one. 4. After 19.0짹13.8 months of follow up after redo-ablation, 11.1% (1/9) of SPVI group and 50.0% (4/8) of 4PVI group recurred AF. Subsequently, AF-free rate of each group was 92.9% (39/42) in SPVI and 88.6% (31/35) in 4PVI(p=NS). Conclusion In patients with clearly documented AF triggering PVs, isolation of only PV triggering AF or ipsilateral PV antrum have comparable success rate to empirical 4 PV isolation with lower number of RF energy delivery and shorter procedure time.