Twenty-eight patients operated with success for isolated coarctation of the aorta (i.e. with normal blood pressure and upper/lower limb gradient < or = 20 mmHg at rest) underwent exercise testing to evaluate blood pressure and upper/lower limb pressure gradient during exercise. At maximum effort: 57% (16/28) of the patients were hypertensive and 43% (12/28) of patients increased upper/lower limb gradient over 35 mmHg. No significant correlation was found between the age at surgery (before or after 3 years of age) and maximal systolic blood pressure on exercise and maximal pressure gradient on exercise. The 12 patients with an exercise pressure gradient > 35 mmHg underwent digital angiography or magnetic resonance of the aorta. In 7 cases a mild residual narrowing was found (5 with mild transverse aortic arch hypoplasia, 2 with a mild residual coarctation). In 5 cases no residual narrowing was present. Many factors are thought to be involved in the anomalous behaviour of blood pressure during effort: in some cases anatomic factors, as residual narrowings of the aorta, in other cases functional factors, as increased forearm vascular reactivity, altered baroceptor function, different reactivity and structure of the pre- and post-stenotic aorta, etc., in other cases finally, both factors, anatomic and functional. We conclude that the exercise testing provides the best information on blood pressure modifications during activity and it allows to us to identify those patients which, because of exercise-induced hypertension, remain at risk of premature cardiovascular disease, also after a successful operation. However, when hypertension is found during effort, a strenous physical activity should be avoided and antihypertensive treatment may be required. So the cardiovascular risk due to hypertension can be reduced in the long term follow-up. Corrective surgery for coarctation of the aorta, introduced in 1944, has completely modified the natural history of the disease. Nowadays the operative risk is very low for isolated coarctation and the great majority of the patients is asymptomatic after surgical repair. Nevertheless, their life expectancy is substantially shortened, if compared with the survival curve of a normal population. The vascular and cardiovascular accidents, usually related to residual systemic hypertension, are the most common cause of this. Some studies in the literature have shown that many patients with normal blood pressure and no or little residual upper/lower limb pressure gradient at rest, may develop an anomalous blood pressure response e and/or a high upper/lower limb pressure gradient during exercise. We have studied by exercise test a group of patients successfully operated on for isolated coarctation of the aorta to evaluate the behaviour of the systolic blood pressure and the upper/lower limb pressure gradient during exercise. The aim was to recognize the patients who, inspite of very good operative result, remain at cardiovascular risk in the long-term follow-up.