Purpose: After noting the colon to be nonfixed and coiled in the pelvis of a patient with colonic atresia and total colonic Hirschsprung's disease, the authors sought to determine whether this colonic position might be predictive of aganglionosis in the atretic colon. Methods: The authors reviewed all cases of colonic atresia treated in their institution over the past 2 decades with regard to colonic orientation and the presence of aganglionosis. Results: We identified 9 patients with colonic atresia. Two of these patients, as well as one patient with ileal atresia, also had long-segment Hirschsprung's disease. All 3 of these patients had foreshortened nonfixed colons located predominantly in the pelvis. None of the other 6 patients with colonic atresia had this configuration. Reviewing 12 reported cases from other institutions of total colonic aganglionosis associated with atresia, 7 appear to have had a pelvic nonfixed colon; colonic orientation could not be determined from the remaining reports. The diagnosis of Hirschsprung's disease was not established in any case before repair of the atresia, and each patient required a secondary enterostomy. Conclusions: An early gestational atresia, occurring before secondary retroperitoneal fixation of the colon at approximately 11 weeks may result in interruption of caudal migration of enteric nerves manifesting as Hirschsprung's disease distal to the atresia. Moreover, the aganglionosis may be predicted by a foreshortened, nonfixed colon coiled in the pelvis. Thus, biopsy of the colon should be performed at initial exploration in all cases of atresia in which the colon is not properly fixated to avoid immediate or delayed anastomosis to an aganglionic colon.