In a follow-up, 2 to 27 years postoperatively, of 43 patients with unilateral choanal atresia a high frequency of relapses was observed. In 47% of the cases, preoperative symptoms had reappeared, and in 84% scar tissue had reduced the choanal opening to less than half of normal size. In most of the patients a transpalatinal approach was used, either ad modum Ruddy, Wilson or Owens. In order to improve the results, the surgical method and the postoperative treatment were changed in a new series of 15 patients with unilateral atresia. These patients, 6 to 26 years of age, were operated on by a transplantinal approach during two months in the autumn of 1974. After removal of the atresia, the posterior part of the nasal cavity was modeled, with a dental drill, to increasing diameter towards epipharynx. To keep the opening patent a PVC tube was left in the choana for six weeks postoperatively. The results were encouraging. Two and a half years after the operation there were no relapses.