Direct pancreatic function tests, such as the secretin-pancreozymin test and the Lundh test, are--by direct measurement of the contents of duodenal secretion following exogenous (hormonal) or endogenous (test meal) stimulation--the best way to assess exocrine pancreatic function. However, these tests are time-consuming, invasive, and expensive, and therefore their use is limited to specialized centers only. Several studies have shown that indirect pancreatic function tests are a practicable alternative to direct pancreatic function tests for diagnosing exocrine pancreatic insufficiency. They allow staging of the disease and thereby facilitate comparison of different studies. They are also useful in some cases for determining whether pancreatic enzyme replacement therapy is necessary or not. In contrast to morphological procedures, they involve neither side effects, risks for the patient, nor complications for patients, investigators, and laboratory staff alike. The procedures being standardized, the test results depend to a lesser extent on the experience of the investigator, and more on the selection of and the instructions to the patient, and to some extent, on the severity of the exocrine pancreatic insufficiency. Like all pancreatic function tests, the indirect tests do not give a clue to etiology nor help investigators to differentiate between pancreatic insufficiency owing to chronic pancreatitis and that owing to pancreatic cancer. The role of pancreatic function tests in diagnosing early chronic pancreatitis in comparison to morphological examinations remains to be established.