The Doppler ultrasound technique has been used to assess the haemodynamics of the peripheral circulation in patients with arterial disease. Using this method the resting pressure index and the response after exercise of the systolic pressure at the ankle was determined in 62 limbs. Following exercise, four patterns of abnormal response to exercise were found and graded in severity from 1 to 4. A single aorto-iliac lesion was associated with a normal or slightly reduced resting pressure index but with a severe reduction of pressure (grade 3-4) after exercise. A single femoropopliteal lesion was usually associated with a low resting pressure index but only a slight (grade 1-2) fall after exercise. A low resting pressure index and a severe postexercise grade were found in patients with multiple occlusions. Disease of the profunda femoris artery was associated usually with both a low resting pressure index and a grade 3-4 post-exercise curve.