The authors studied flow in the internal mammary artery by Doppler ultrasonography after bypass surgery of the left anterior descending artery to determine the correlation between the flow pattern and the quality of the distal run off. A pulsed Doppler was used to record flow from the right and left internal mammary arteries in the first, second and third intercostal spaces and the supraclavicular fossa. Only the best quality recordings with the highest amplitudes were retained for analysis. Forty-nine patients (average age 61 +/- 10 years), 43 men and 6 women, were included and were examined between the 10th and 15th postoperative days. All had stenosis of the left anterior descending on coronary angiography: three subgroups were identified ad the time of evaluation: (I) revascularisation of an infarcted zone with important angiographic and echographic sequellae. (II) revascularised zones with slight wall motion abnormalities. (IIIa) revascularisation of myocardium with no abnormality (including a subgroup of 5 patients (IIIb) characterised by a postoperative low output state and echocardiographic changes not present before surgery). Significant changes were observed in the flow patterns of the different groups. (I) an exclusively systolic flow (diastolic velocity time integral = 2.85 cm), (II) systolodiastolic flow (diastolic velocity time interval = 9 cm) similar to that in group IIIb, and IIIa predominantly diastolic flow (diastolic velocity time integral = 15.2 cm). The amplitude of diastolic flow in the mammary artery graft was therefore related to previous ischaemia of the revascularised myocardium; detection of stenosis by Doppler ultrasonography should therefore take into account the previous history of the patient.