Salivary and pancreatic isoamylases in duodenal aspirates obtained during assessment of pancreatic function after test meal stimulation were separated by agarose gel electrophoresis. Salivary amylase was found to be a constituent of the duodenal aspirates in more than 75% of the tests. The mean relative contribution of salivary amylase to the total amylase activity of the aspirates varied from about 15% in normals to about 40% in patients with chronic pancreatitis and pancreatic carcinoma. The amount of salivary amylase varied widely not only between the individuals but also within the samples of the same test series. Specific determination of the pancreatic isoamylases instead of determination of the total amylase increased the discrimination between normals and patients with pancreatic dysfunction.