Chronic pancreatitis is a well-defined disease on histopathological grounds, but for clinical purposes diagnosis is generally not based on histological specimens. Imaging procedures, non-invasive or with different degrees of invasiveness, and pancreatic function tests are therefore the diagnostic mainstay in patients with suggestive clinical history. The correct diagnosis of chronic pancreatitis is easy in late stages but difficult in an early stage of the disease. A particular challenge is the differentiation between acute or recurrent acute and early chronic pancreatitis. Earlier classifications (Cambridge and Marseille) did not consider the complex interrelationship between (especially alcoholic) acute and chronic pancreatitis. A possible solution is to separate the entities into probable and definite alcoholic chronic pancreatitis, with the assignment into the latter category achieved by follow-up investigations. Up to now the best diagnostic accuracy at an early stage is achieved by the detection of abnormalities of the ductal system in endoscopic retrograde pancreatography or by assessing exocrine function with the secretin-ceruletide test. The endoscopic ultrasound may substitute the endoscopic retrograde pancreatography as superior imaging modality that detects both parenchymal and ductal changes of chronic pancreatitis at an early stage. Magnetic resonance pancreatography is a further promising diagnostic tool without the risk of pancreatitis after endoscopic retrograde pancreatography, but imaging of the side branches, which is crucial for detection of early chronic pancreatitis, is not yet sufficient. Faecal elastase is a progress in non-invasive testing of exocrine pancreatic function, but its value for the diagnosis of chronic pancreatitis under conditions of clinical practice is limited. Several (13)C breath tests have been developed, but their availability and their diagnostic accuracy in chronic pancreatitis is still limited. Light to moderate exocrine pancreatic insufficiency is not detectable with adequate accuracy by tubeless function tests. A specific serum marker of pancreatic fibrosis which would reliably indicate the presence of chronic pancreatitis or its progression to is not available.