The total daily amount of extractable cationic trypsin, chymotrypsin, and pancreatic elastase 2 in feces and ileostomy fluids has been studied in normal individuals and healthy colectomized subjects. Quantitation was performed using immunological assays with polyethylene glycol as a fecal marker. The extractable amount of each of these enzymes in the feces of normal individuals was less than 1 mg/24 h. However, in fecal extracts from antibiotic-treated normal individuals a 100-fold increase in immunoreactive cationic trypsin was observed, while chymotrypsin and elastase 2 were only 2- to 3-fold higher. In extracts from ileostomy fluids cationic trypsin, elastase, and chymotrypsin all showed mean values in the order of 50-200 mg/24 h. The characterization of the immunoreactivity of pancreatic proteases showed no qualitative differences when measured in duodenal juice or fecal and ileostomy extracts.