Background: Coronary flow reserve (CFR) and fractional flow reserve (FFR) provide complementary information on the coronary circulation. Using a pressure wire, it is possible to calculate CFR by thermodilution (CFRthermo), so that FFR and CFR can be measured with a single guide wire. The present multicentric study was performed to compare the feasibility of CFR thermo obtained with an improved algorithm and a standardized injection technique and its agreement with Doppler-derived CFR (CFR Doppler). Methods and results: In 86 patients with coronary artery disease recruited during 1 week in eight centres FFR, CFRthermo and CFRDoppler were measured. FFR could be obtained in all patients (100%). An optimal CFRDoppler could be obtained in 69% of the patients. CFRthermo could be obtained in 97% of the patients. A significant correlation was found between CFRDoppler and CFR thermo (r=0.79, P<0.0001) but CFRthermo tended to be higher than CFRDoppler. Conclusions: In a setting close to 'real world' practice, this multicentric study confirms the feasibility and reliability of thermodilution-derived CFR. In addition, the safety and the swiftness of assessing FFR and CFR with one single guide wire makes the latter a unique clinical tool for the evaluation of the coronary circulation.