We describe the generation of an expressed sequence tag (EST) database of the mouse organ of Corti (OC). Over 20,000 independent clones were isolated, analyzed, and grouped into 8690 unique gene clusters. A large pool of novel genes unique to the OC was identified. Sequence alignments frequently revealed alternatively spliced forms of known genes potentially relevant in the OC function. We have also electronically mapped a subset of OC mouse ESTs to several syntenic regions associated with human autosomal and recessive deafness, which may prove useful for the identification of new positional candidates for these human diseases. The EST dataset is available as an interactive Web-based public database at. This resource provides both a view of the profile of gene expression in the OC at the onset of hearing and a tool to identify novel genes of importance in hearing.