Traumatic intercostal pulmonary hernia is a rare sequel to injury, especially in children and where there is no penetrating wound. Spontaneous regression of these hernias has been reported and conservative management has been advocated. We describe a case in which a smooth-walled intercostal defect and lung hernia that did not regress developed in a child. This was successfully repaired with a Gore-Tex (expanded polytetrafluoroethylene) patch. Repair is advisable in such cases, but operation can be delayed to allow possible resolution.