Transit-time Doppler can be used for intraoperative assessment of graft patency, by measuring conduit flow, or from the calculation of a derivation of the spectral waveform. The optimal timing of measurement is when graft flows are maximal. Fifteen patients underwent multivessel coronary bypass surgery without the use of cardiopulmonary bypass. Transit-time Doppler of 57 anastomoses was performed immediately before and after release of the Octopus stabilizing device, and mean graft flow was measured as over 5 consecutive beats. The graft flow increased after release of the stabilizing device for all grafts from 20.1+/-1.8 to 33.2+/-2.4 ml/min (P<0.001). When analyzed by individual grafts, and by coronary artery territory, the increase in flow remained significant. The timing of transit-time Doppler assessment of conduit flow should be performed immediately after release of the stabilizing device.