The fat-soluble vitamin contents in the blood (vitamins A, D, E, and K) were determined in 12 patients with chronic pancreatitis (exocrine pancreatic insufficiency) and in 20 healthy adults by the HPLC and CPBA methods. In addition, 9 g (3 g x 3 times) of high potency pancreatin was given to 11 patients with chronic pancreatitis (CP) for approximately 1 month and changes in the blood fat-soluble vitamin levels were evaluated before and after the treatment. The major component of vitamin E was alpha-tocopherol. The mean alpha-tocopherol level in normal individuals was 0.97 mg/dl, while it was significantly reduced in CP patients (p < 0.01). The vitamin A, D, and K levels had also been reduced in patients with CP, but the differences were not significant (although some patients in this group exhibited significant reductions from the levels of normal individuals). Only the blood vitamin E level showed a significant correlation with the fecal fat excretion or the fat absorption rate. None of the patients with CP exhibited an overt fat-soluble vitamin deficiency (i.e., the deficiency of fat-soluble vitamins was at a subclinical level). These results indicated that CP patients suffer from a latent fat-soluble vitamin deficiency and that the vitamin E level is closely related to a dysfunction of fat digestion. It was suggested that the dietary intake of each fat-soluble vitamin should be evaluated further.