The mRNA expression of the neuronal nicotinic acetylcholine receptor subunits was determined in adult rat vestibular end-organs and in Scarpa's ganglion (SCG) by in situ hybridization with [35S] riboprobes. Neurons in the SCG expressed the alpha 4-7 and beta 2-3 mRNAs, but not alpha 3 or beta 4 mRNAs. Not all SCG neurons expressed every mRNA found in SCG. The alpha 6 and beta 2-3 riboprobes labeled all neurons, but alpha 4, alpha 5, and alpha 7 mRNAs were selectively expressed in one or more subpopulations of SCG neurons. Vestibular sensory hair cells, in contrast, expressed only alpha 9 mRNA.