The effects of cardiac surgery on patients with congenital heart defects and the subsequent development of scoliosis were studied. A group of 998 patients with congenital heart defects who were less than sixteen years old were operated on at the Mayo Clinic during the ten-year period 1950 through 1959. Standing roentgenograms of the spine were made of 377 of the patients ten years or more after surgery. The ages of the patients at follow-up ranged from ten years and seven months to thirty-five years and three months, with a mean age of twenty-one years and four months. The average length of follow-up was fourteen years and eleven months. Of the 377 patients, thirty-two (8.5 per cent) had curves greater than 20 degrees. The female:male ratio of patients with congenital heart defects was 1:1, whereas of those who developed scoliosis it was 5:3. There was no correlation between scoliosis and the following: patient's sex, cardiac abnormality, size or side of the heart, side of the aortic arch, presence of cyanosis, age at surgery, number and type of surgical incisions, number and side of ribs removed, or number and type of surgical procedures.