An individual who has cystic fibrosis (CF) may suffer from gastrointestinal problems related to inadequately controlled intestinal absorption secondary to the pancreatic insufficiency. These include neonatal meconium ileus, distal intestinal obstruction syndrome (DIOS), constipation and acquired megacolon, rectal prolapse and rarely pancreatitis. If the intestinal malabsorption is well controlled with an effective pancreatic enzyme preparation, DIOS, constipation and rectal prolapse are infrequent. Persisting gastrointestinal symptoms should be investigated thoroughly to exclude other disorders not directly related to the cystic fibrosis; these include cows' milk intolerance, coeliac disease, giardiasis, Crohn's disease and intra-abdominal malignancy. Both appendicitis and intussusception may cause difficult diagnostic problems particularly in patients who may also have distal ileal obstruction syndrome.