Background : The factors which predict post percutaneous transluminal renal angioplasty (PTRA) BP response were still unknown. The purpose of this study is to investigate that renal artery fractional flow reserve(FFR) is related to BP response after PTRA. Methods : Target lesions were renal artery stenosis more than 50% in diameter stenosis. Prior to PTRA, baseline, hyperemic FFR were checked with pressure wire. (Radi짰) Hyperemia was induced intrarenal 300ug nitroglycerin injection. FFR measurements were repeated after PTRA. Blood pressure was measured pre and post PTRA and 1 month later. The number of antihypertensives was analysed. Results : 27 patients, 31 lesions were included. BP response(SBP reduction by ���20mmHg, DBP reduction by ��� 10mmHg or reduction of antihypertensive dose) was shown only in 14 patients (52%) on day 1, 12 patients (44%) on day 30. Responders on day 30 were younger (57짹20 vs 70짹7, p=0.03) more severely hypertensive (SBP 146짹18 vs 131짹16mmHg, p=0.06; DBP 83짹11 vs 72짹8mmHg, p0.006). Responders showed lower SBP and BP decrease than nonresponders (120짹12 vs 138짹16mmHg, p=0.003; SBP ��� -26짹24 vs 5짹17mmHg, p=0.007; DBP -10짹12 vs 6짹8mmHg, p=0.001) Responders showed lower baseline FFR (0.72짹0.24 vs 0.89짹0.12, p=0.077) and 87.5% of patients with FFR below 0.7 had BP improvement on day 30. Conclusion : PrePTRA FFR < 0.7 can be a useful marker for selecting patients who would have BP response after renal artery angioplasty (88% positive predictability 1 month later) It can help avoiding unnecessary PTRA.