362 patients operated upon for coarctation of the aorta from 1961-1980 were analyzed retrospectively. Age at operation was less than 2 years in 74 (group A) and greater than or equal to 2 years in 288 patients (group B). Associated cardiovascular malformations were common, especially in group A patients. Early mortality was 12.2% for group A and 1.4% for group B patients. 336 patients were followed for 6 months to 21 years (mean 8.9 years). Late mortality was 0.8% per patient year. Associated cardiac defects and postoperative hypertension were responsible for most of the late deaths. Late reoperations were performed because of aortic valve disease, residual coarctation (with persistent hypertension) and aortic aneurysms at the site of anastomosis. The incidence of hypertension decreased from 82.5% preoperatively to 33.5% at discharge from the hospital. It decreased further during follow-up in patients operated less than 10 years of age, but remained constant in the older patients. In conclusion, morbidity and mortality after operative repair of coarctation are determined mainly by (1) associated cardiac malformations, and (2) postoperative hypertension. Patients with isolated coarctation and postoperative normal blood pressure have an excellent prognosis. Patients operated upon from between 2-9 years of age carry the lowest risk for residual coarctation and late postoperative hypertension.