The assay of pancreatic triglyceride lipase (PL) is done routinely in clinical laboratories and in research laboratories with an interest in this lipolytic enzyme. The assay requirements differ between these two settings. The clinical laboratory requires automated assays that are specific, sensitive, fast, and reproducible. Conversely, researchers interested in PL do not require automated assays, but need specific, sensitive, and reproducible assays that allow them the flexibility to vary assay conditions. Researchers may also require assays of colipase, a small pancreatic protein that is necessary for PL activity in the duodenum. These requirements have led to the development of many different PL assays, many suited only for the clinical laboratory. The remainder of the Introduction will discuss methods utilized in both settings, and then two assays suitable primarily for the research laboratory are described in Subheadings 3.1. and 3.2., including the assay of colipase in Subheading 3.3.