Anastomosis of the left internal mammary artery to the left anterior descending artery was performed in 9 pigs to evaluate the effect of changes in the cardiac cycle and the choice of ultrasound mode on assessment of graft morphology. The length of the anastomosis and the diameters of the left anterior descending artery at the toe and heel of the anastomosis, as well as downstream, were measured in end-systole and end-diastole with both B-mode and color Doppler imaging. None of the diameters were influenced by the cardiac cycle using either ultrasound mode. B-mode yielded larger diameters at all points except the toe of the anastomosis. It was concluded that provided the scanning is perpendicular to the vessel, the morphology of an anastomosis can be assessed without paying much attention to the phase of the cycle or the mode of ultrasound applied.