Although the exocrine pancreatic function test (PFD) using a synthetic peptide is a simple and useful test, it often gives a false positive result in hepatic diseases, renal diseases, and gastrointestinal diseases. Attempts were made to solve this problem. PFD combined with the PABA test, PFD combined with the D-xylose test as well as PFD alone were consecutively performed in 15 healthy controls, 15 patients with chronic pancreatitis, 15 with chronic hepatic diseases, 14 with chronic renal diseases and 16 with gastrointestinal diseases. Results of the tests were interpreted according to the following three criteria indicating exocrine pancreatic dysfunction: (A) an abnormal PFD with normal PABA or normal D-xylose test value, (B) a decreased PFD/PABA ratio or PFD/D-xylose ratio and (C) a large difference between PABA and PFD or a small difference between PFD and D-xylose. Specificity and sensitivity, were evaluated. PFD with the PABA test and PFD with the D-xylose test are very useful for avoiding false results. Criterion (A) with the PFD and PABA tests is the most suitable for the evaluation of exocrine pancreatic function in patients with possible hepatic, renal and gastrointestinal diseases. Criterion (A) with the PFD and D-xylose tests is almost as useful.