The short- and long-term results of effective surgical repair of coarctation of the aorta on left ventricular mass and function in 48 patients were evaluated using echocardiography and stress-gated radionuclide angiography. Thirty-two of the 48 patients who had no additional cardiac problems and had technically adequate radionuclide angiograms form the basis for this report. Among these, three had mild systolic hypertension and none had significant aortic valve dysfunction. Age at the time of study ranged from 6.5 to 59 years (mean 27). Age at the time of surgery ranged from 3 months to 34 years (mean 12 years). Duration from surgery to the time of noninvasive study ranged from 2 to 29 years (mean 15). In the 32 patients, left ventricular mass was 120 +/- 20 g/m2, compared with a control value of 87 +/- 10 g/m2. Mean left ventricular ejection fraction was elevated to 69.2 +/- 1.6% at rest (control 60 +/- 1.3%) and 78.8 +/- 1.3% during exercise (control 70 +/- 1.7%) (p less than 0.01). The systolic ejection rate was significantly increased (p less than 0.01) and end-systolic volume significantly decreased (p less than 0.01) compared with values in control patients. There was no correlation between ejection fraction and either age at the time of surgery or years since surgery. These findings of hyperdynamic left ventricular function and increased left ventricular mass without apparent cause many years after coarctation repair raise important questions as to mechanisms, extension to other forms of afterload stress that have been surgically or medically relieved and long-term outcome.