Background Complex use of arterial conduits has resurrected concerns about the adequacy of conduit flow. The T-graft is the extreme example of this trend. Our purpose was to identify the limitation of single source inflow and to compare flow capacity with completion coronary flow. Methods Between February 1999 and November 2001, 372 patients underwent total arterial revascularization with the T-graft alone. Intraoperative flows were recorded for each limb of the T-graft before and after distal anastomoses in 204 patients. Independent predictors of T-graft flow were identified by multivariate analysis. Results Free flow for the radial arterial (RA) limb was 161 ± 81 mL/min, the internal thoracic artery (ITA) limb 137 ± 57 mL/min (combined 298 ± 101 mL/min) versus simultaneous limb flow of 226 ± 84 mL/min giving a flow restriction of 24% ± 14%. Completion coronary flow was 88 ± 49 mL/min for the RA, 60 ± 45 mL/min for the ITA, and 140 ± 70 mL/min for both limbs simultaneously to give a flow reserve (vs simultaneous free flow) of 160% or 1.6. Independent predictors of completion RA limb flow are RA proximal diameter (p = 0.005), number of anastomoses (p = 0.018), and target stenosis (p = 0.005). Conclusions A flow reserve of 1.6 compares favorably with an ITA flow reserve of 1.8 at 1-month postoperatively and 1.8 for both the ITA T-graft and the ITA/RA T-graft at 1-week postoperatively as reported by others. Proximal RA diameter and competitive coronary flow influence completion T-graft flow. These data quantitate the limitation of single source inflow of the T-graft configuration and support its continued use.