In this paper, Doppler continuous-wave analysis of blood velocity in the internal mammary artery, anastomosed to the left coronary vascular bed in humans who have undergone myocardial revascularization, is proposed as a non-invasive technique to study coronary blood flow during physiological procedures which cause it to change. Blood velocity curves obtained in normal and anastomosed internal mammary arteries were compared during hyperventilation and the Valsalva manoeuvre. During hyperventilation, blood velocity increased in the normal mammary but not in the anastomosed artery. During the expiratory effort of the Valsalva manoeuvre, the mean blood velocity decreased in the normal mammary artery but it did not change significantly in the anastomosed artery. Variations in the mean velocity were largely prevented by simultaneous and well-balanced increases and decreases in the diastolic and systolic velocities, respectively.