Dietary fats are essential for life and good health. Efficient absorption of dietary fats is dependent on the action of pancreatic triglyceride lipase. In the last few years, large advances have been made in describing the structure and lipolytic mechanism of human pancreatic triglyceride lipase and of colipase, another pancreatic protein that interacts with pancreatic triglyceride lipase and that is required for lipase activity in the duodenum. This review discusses the advances made in protein structure and in understanding the relationships of structure to function of pancreatic triglyceride lipase and colipase.