Three new cases of patients with co-occurrence of colonic atresia and Hirschsprung's disease and a review of the literature (n = 5) are presented in this report. All patients (n = 8) except one were full-term infants who had no other significant anomalies. The preterm infant had associated tetralogy of Fallot in addition to Hirschsprung's disease and colonic atresia. Six patients had atresia of the ascending colon, and two had atresia of the colon to splenic flexure. All colonic atresias were diagnosed neonatally; however, there was mean delay of 15.4 months (range, 1 mo to 5 years) in diagnosing associated Hirschsprung's disease. There were two deaths. A careful examination of the resected specimen to rule out Hirschsprung's disease is recommended. Performing a rectal biopsy must be considered for patients who initially were treated for colonic atresia and who have a slow return of normal gut function.