With a view to improve the diagnosis of salivary gland diseases (in particular, Sjögrén's syndrome) associated with decreased salivary gland function and decreased stimulated salivary gland response, the normal range of radionuclide uptake function and the stimulated salivary gland response were established in 27 subjects without any known salivary gland disease. Following injection of 99Tcm-pertechnetate, sequential images were recorded for 40 min with oral administration of citric acid at 30 min. The total uptake index (TUI) was calculated as the sum of the background corrected count rates over the parotid and submandibular glands at 3 min divided by the injected dose. The TUI, expressed as a percentage of dose, was 0.55 +/- 0.12 (mean +/- S.D.). The stimulated salivary gland response (SSGR) was calculated as the difference between the rate constants (min-1) of monoexponential fits to the time-activity curves over the four salivary glands immediately after and before the administration of citric acid. The lower significance limit (P < 0.05) of the SSGR was a 2.4% decrease per min. The parameters TUI and SSGR can be used as a diagnostic tool in, for example, early Sjögren's syndrome.