A simple evocative test has been used to study pancreatic function. Serial estimations of amylase and lipase in blood serum are made at intervals up to six hours and again at 24 hours after injecting intravenously standard doses of secretin and pancreozymin. The results of 213 tests on a normal group, in pancreatic disease, in biliary and hepatic diseases have been analysed and compared with the results of duodenal intubation and an oral glucose tolerance test. A combined evocative test and oral glucose tolerance test provide evidence of pancreatic dysfunction in the majority of cases of cancer of the pancreas and chronic pancreatitis. The conditions of the test are described and the pathological lesions in which false positive evocative tests may be found are indicated. The simple evocative test provides the earliest biochemical evidence of pancreatic disease in some patients with cancer of the pancreas and chronic pancreatitis.