ABSTRACT.Pancreatic exocrine insufficiency is an important factor in the malabsorption of cystic fibrosis, but other factors may also contribute to the steatorrhoea. It has been suggested that thickened mucinous covering of the villi forms a mechanical barrier to absorption. A double blind cross‐over placebo controlled trial of the oral mucolytic agent N‐acetylcysteine failed to improve the fat malabsorpt