Short-chain carboxylic acids in the feces of 12 patients with chronic pancreatitis having steatorrhea and 18 healthy subjects were determined by high-performance liquid chromatography. The fecal amount of the patients with chronic pancreatitis was increased to about twice that of the control, and the fat in the feces increased to eight times. The excretion of short-chain carboxylic acids increased to about three times. The short-chain carboxylic acid concentration regarded as derived from protein or amino acid, such as iso-butyrate, isovalerate, and n-valerate, was significantly increased in patients with chronic pancreatitis. From the above results, our data suggest that there is maldigestion of protein besides that of carbohydrate. And we confirmed that these data are an in-vivo illustration of the phenomena which have been studied in-vitro experiments, when fecal bacteria were incubated with peptide or amino acids as a substrate.