Two experiments were conducted to ascertain the relationship between serum and parotid fluid uric acid levels. Samples of blood and parotid fluid were collected from six healthy young adult males, both before and during a 5-day period in which probenecid, a uricosuric drug, was administered. In the second experiment, parotid fluid and blood samples were collected from two subjects undergoing haemodialysis on the artificial kidney. The experimental procedures brought about sharp decreases in serum and parotid fluid uric acid for all subjects. A highly significant correlation was found between serum and parotid fluid uric acid levels.