Background: According to European Association for Cardio-Thoracic Surgery (EACTS) and European Society of Cardiology (ESC) guidelines, Transit time flowmetry (TTFM) is recommended for intraoperative graft patency verification during coronary artery bypass grafting (CABG). Studies are done to find out the accuracy and precision of the TTFM technique to measure left internal mammary artery (LIMA) blood flow when compared to its free flow. But none of the studies have been done so far on saphenous vein graft (SVG) graft flow measurement accuracy and precision with TTFM technique when compared to free flow measurement. Methods: The TTFM flow measurement and free blood flows was evaluated in 48 SVG grafts in patients undergoing beating heart coronary artery bypass surgery (OPCABG) using SVG as one of a conduit. The measurements were done after doing proximal anastomosis of SVG to aorta and before doing distal coronary anastomosis. Simultaneous reading was taken with TTFM devise and free flow through the graft. Results:The TTFM reading and free flow measurement results difference where statistically not different. Conclusions: The difference between TTFM measurements and free flow measurements were statistically not significant. TTFM can be Taken as an accurate indicator of SVG flow during CABG with clinically acceptable precision.