Peripheral cranial sensory nerves projecting into the oral cavity receive food intake stimuli and transmit sensory signals to the central nervous system. To describe and compare the features of the cranial sensory ganglia that innervate the oral cavity, i.e., the trigeminal, petrosal, and geniculate ganglia (TG, PG, and GG, respectively), in situ hybridization was conducted using riboprobes for neurotrophin receptors (TrkA, TrkB, and TrkC), a neurotransmitter (substance P), and ion channels important for thermosensation (VR1 and TREK-1). In TG, all in six probes yielded positive signals to various extent in intensity and frequency. In addition, a strong correlation between the expression of VR1 and those of TrkA and substance P was observed as in the case of the dorsal root ganglia. In PG, positive signals to all six probes were also detected, and the correlation of expression was similar to that shown by TG. On the other hand, most cells in GG were positive to the TrkB probe, and a small number of cells were positive to the TrkC probe, but no significant signal was observed for the other four probes. These results indicate that TG and PG consist of cells that are heterogeneous in terms of neurotrophin requirement and somatosensory functions, and that GG seems to consist mainly of a homogeneous cell type, gustatory neurons. In conclusion, TG, PG, and GG, show gene expression characteristics intrinsic to the three ganglia. It is also concluded that TG and a portion of PG project several types of somatosensory nerves. This is consistent with the finding that GG and a portion of PG project gustatory nerves.