Between 1957 and 1980 reoperation for coarctation of the aorta was performed in 21 patients at one institution for an overall incidence rate of 7.9 percent. The incidence rate of reoperation was 38 percent for patients younger than age 3 years and 1.5 percent for patients 3 years or older at initial repair. Before reoperation 14 of the 21 patients were symptomatic, 19 had systolic hypertension of the upper limbs and 20 had a documented coarctation pressure gradient at rest (mean 42.4 mm Hg). Surgical techniques used at reoperation were patch aortoplasty in 12 patients, graft interposition in 4, end to end anastomosis in 3 and end to side left subclavian to descending aorta bypass graft in 2. There was one surgical death. The 20 survivors have been followed up a mean of 4.3 years. There has been significant symptomatic improvement (p < 0.001). Upper limb hypertension has also lessened significantly (p < 0.001) after reoperation;15 patients are no longer hypertensive and 3 have a lesser degree of hypertension. The coarctation pressure gradient at rest has significantly decreased (p < 0.001); 13 patients have no residual gradient and 7 have a mild gradient of 20 mm Hg or less. Graded treadmill exercise testing performed in five patients after reoperation documented upper limb hypertension in four and a marked increase in coarctation gradient with exercise in three. In conclusion, the incidence of reoperation is significantly increased in patients who are younger than age 3 years at initial coarctation repair. Reoperation is a safe and effective procedure. It has a low mortality rate (4.8 percent), relieves symptoms and decreases hypertension and the coarctation pressure gradient. Patch aortoplasty appears to be the operative procedure of choice. Moderate to severe hemodynamic abnormalities may persist during exercise after reoperation for coarctation of the aorta.