It is generally accepted that there are five basic gustatory qualities, i.e. sour, salt, sweet, bitter and umami and there is a dose-response reflex parotid salivary secretion that exists for each of these stimuli. When these stimuli are mixed together interactions may occur in a suppressive, additive or synergistic manner. The simplest of these are binary interactions. The interactions between mixtures of two different stimuli using the gustatory-parotid salivary reflex have only been examined in a few studies. The aim of this study is to examine the effect of mixtures of sucrose with monosodium glutamate (MSG) or sodium chloride (NaCl) on reflex parotid salivary secretion in man. With local ethics committee approval, salivary flows were recorded using Lashley cups and cannulae connected to an instantaneous flow meter. Gustatory stimuli used were solution of MSG (0.01 and 0.03M), sucrose (0.1 and 0.5M), NaCl (0.1 and 0.3M) alone and as mixtures of sucrose-MSG or sucrose-NaCl. The mixtures contained the same molar concentrations as those presented singularly. Stimuli were applied for 30s, and repeated following washout with water and when salivary flows had returned to resting levels. The stimuli were first presented as single solutions, followed by the mixtures. Each group of stimuli was repeated twice. The salivary flows to the single stimuli were added together to give a calculated additive flow for the mixture. Large variation in the salivary flows of individual subjects meant that salivary flows were normalised as a percentage of the calculated flow. The normalised results for the mean salivary flow for the sucrose-MSG mixtures compared to the calculated flows for these mixtures was significantly different (mean ± s.e., 81.2 % ± 3.4, P0.1; paired t-test, n=7). The observation that the flow produced by the sucrose-MSG mixture did not reach the additive response level suggests that some degree of suppression is occurring within the gustatory-salivary reflex pathways with these basic stimuli. Furthermore the salivary responses to mixtures of sucrose-NaCl were not significantly different from the calculated flow and this would suggest that there is an additive response within the gustatory-salivary reflex with these basic stimuli.