The authors consider the different strategies in long term enzyme replacement therapy in relation to the complex mechanics at the basis of pancreas exocrine insufficiency. This condition occurs in chronic pancreatitis and is present in Cystic Fibrosis, the most common potentially lethal inherited disorder of Caucasians. Pancreatic exocrine insufficiency occurs in the vast majority of cystic fibrosis affected children and is now becoming a frequent pathology in adults for the better life expectancy and the recent acknowledgements in this disease. The principal aims of research in enzyme replacement therapy have been directed at the formulation of products with high enzyme concentration, to the prevention of gastric acid inactivation of enzymes and to the better mixing of the preparations with meals. The authors consider all the different enzyme preparations from pancreatin powder to the 1st. generation of enteric coated tablets and examine the advantages of administering H-2 receptor antagonists or antacids and the possibility of stimulating bicarbonate secretion as an adjunct to pancreatic enzyme replacement therapy. Significant benefits in pancreatic insufficiency therapy have derived from the introduction of enteric coated microspheres which ensure a consistent level of enzymes to reach the duodenum mixed with the meal and which are resistant to gastric acid inactivation as well.