Summary: I reviewed the literature (1966-1994) concerning gastrointestinal (GI) pH, motility/transit, and permeability in cystic fibrosis (CF). Most studies reported were performed with very small numbers of patients, but even when considered together the published data do not confirm some generally expressed views on these topics. The only clear findings were a high incidence of gastroesophageal reflux in CF; pre- and postprandial duodenal pH is 1-2 U lower in patients with CF than in healthy controls; and small intestinal paracellular permeability is 4-10 times greater than normal in CF. Some patients showed abnormalities of lower esophageal sphincter pressure and of esophageal motility, but apart from one case study other disturbances of GI motility have not been reported. The results of hydrogen breath tests strongly suggest that oro-cecal transit is slowed in CF, but these results must be confirmed by an alternative test. Measurements of colonic transit and colonic permeability have not been reported. The few studies of gastric emptying reported are controversial. Whether GI pH, apart from duodenal pH, is normal in CF or whether a subset of patients has exceptionally acid intestinal contents requiring specialized pancreatic enzyme supplementation to normalize digestion is not clear. Finally, I briefly discuss the findings in relation to their possible impact on the pathogenesis of fibrosing colonopathy.