1. The glossopharyngeal nerve response in the rat to taste and thermal stimulation of the posterior third of the tongue was recorded.
2. The nerve shows responses to 0.25-4 M NaCl, 0.5 M KCl and 0.02 M quinine hydrochloride, and very slight responses to 0.5 M sucrose and 0.01 NHCl but no response to water was obtained.
3. The response magnitude for NaCl increases linearly with the logarithm of the concentration up to 4 M.
4. The magnitude of response to 0.02 M quinine relative to that to 0.5 M NaCl is greater than that in the chorda tympani, and the relative magnitude of response for KCl is also greater than that in the chorda tympani.
5. The response to various taste stimuli has a latency of a few sec, the latency for 0.5 M NaCl being 2.5 sec, and shows a characteristic gradual time course.
6. The nerve responds well to both cooling and warming of the tongue, and it has been suggested that this nerve contains both cold and warm fibers.