Colonic gas cysts invariably shrink and disappear and symptoms associated with them resolve if an adequate concentration of oxygen is inhaled over a sufficient period of time. Careful monitoring of inhaled oxygen levels and arterial oxygen tension is necessary to ensure effective therapy. Plain X-ray of the abdomen is the best method of assessing the size and response of the cysts to treatment and for following the patients subsequently. Six consecutive patients managed in this way are discussed and their subsequent progress is documented.