Systemic intraarterial blood pressure and heart rate have been measured during exercise on a foot ergometer in 13 patients suffering from unilateral intermittent claudication. Each limb was exercised separately for 5 min. Both systolic and diastolic blood pressure increased to significantly higher levels during exercise with the diseased limbs than during exercise with the nondiseased limbs. No significant difference was found in heart rate. After cessation of exercise the blood pressure and heart rate dropped abruptly. For the first 2 min of recovery the systolic blood pressure in the diseased limbs stayed higher than the pressure measured at rest immediately before exercise. Ten patients were also exercised for 2 or 3 min with arrested circulation. During this period no significant differences between the diseased and nondiseased limbs were found in relation to blood pressure or heart rate.