The mammalian olfactory system utilizes a biochemical cascade mediated by specialized proteins to detect odorants with high sensitivity and specificity. The recent identification of olfactory neuron-specific components for each step in the signalling cascade suggests that expression of these proteins is coordinately controlled by cis-acting regulatory sequences and trans-acting transcriptional activators. We have used molecular genetic methods to characterize sequences encoding tissue-specific DNA-binding sites in the genes for components of the odorant transduction pathway and have identified a putative transcription factor, Olf-1, that functions at these sites to regulate gene expression.