Salivary and pancreatic amylases in duodenal aspirates were quantitated in 419 consecutive tests performed on 378 patients suspected of having insufficiency of the exocrine pancreatic function. Salivary amylase was detected in samples from 31% of the tests. However, the amount of salivary amylase was sufficient to cause a misinterpretation in 13 tests only. Five of these tests originated from patients with a history of surgery for peptic ulcer disease. This group of patients tended to have large amounts of salivary amylase in the duodenal aspirates. In the unoperated patients (n = 336) 200 tests yielded values for the total amylase concentration above the lower level of the reference interval, and only in 8 of these tests (4%) did correction for salivary amylase change the results to values below the reference interval. It it concluded that quantitation of isoamylase activity in duodenal samples is unlikely to be of significant value in patients without a history of surgery for peptic ulcer disease.