Background: Adenosine is currently used to induce maximal hyperemia for fractional flow reserve measurements (FFR). Bolus intracoronary administration of adenosine is sometimes inadequate for the induction of maximal hyperemia and the duration of the hyperemia is too short for further physiologic studies. Intravenous (IV) adenosine infusion offers sufficient hyperemia and hyperemic time, but, it requires central or large vein access and is unsuitable for cases of transradial approach. Thus, we investigated the safety and efficacy of central venous continuous adenosine infusion using forearm vein access. Methods: Patients who underwent transradial coronary intervention with physiologic studies including FFR, index of microvascular resistance measurements or pressure pullback maneuver were enrolled in this study. We punctured forearm vein and introduced 4 French guiding sheath. A 4 French Judkins right (JR) 3.5 diagnostic catheter was inserted into right atrium using 0.035 inch Terumo guidewire. After FFR measurement with intracoronary bolus adenosine administration (left coronary system: 80ug, right coronary artery: 40ug), FFR was measured again with continuous infusion (140ug/kg/min) into right atrium using the JR catheter and additional physiologic studies were performed if necessary. Results: A total of 14 patients were enrolled. In 5 patients (35.7%), we can make venous access in same drape window with radial artery access. In the other 9 patients, additional drape window was required in the forearm for successful vein access. By the infusion protocol, rapid (25 4.5 sec) and adequate hyperemia was achieved in 14 patients (100%). In 8 patients (57.1%), nonfatal events were occurred including marked bradycardia, hypotension, chest pain or dizziness and they were promptly recovered after infusion stop. No complication was occurred after the procedure including access site problem, vascular damage or cardiac damage. Conclusion: Central venous continuous adenosine infusion using forearm vein access seems to be a safe and effective method of inducing maximal hyperemia for coronary physiologic studies.