The exquisite performance of the mammalian hearing organ results from a finely orchestrated array of cell types, and their highly specialized functions are determined by their gene expression profile. In rodents, this profile is established mainly during the first 2 weeks of postnatal maturation. In this paper, we used the differential display technique on the rat organ of Corti to uncover transcripts upregulated in expression between postnatal stages P0 and P14. A total of 176 different genes were identified, the mRNA amount of which increased during early postnatal development. The transcripts code for proteins serving a broad spectrum of cellular functions including intracellular signaling, control of growth/differentiation, regulation of protein synthesis/degradation/modification, metabolism and synaptic function. In addition, the set of upregulated transcripts contained several proteins of yet unknown function, as well as hypothetical proteins and so far unknown mRNA sequences. Thus, this study unravels the broad and specific transcription program that operates the maturation of the mammalian hearing organ. Further, as 49 of the genes found here map to at least one unspecified deafness locus, our study provides candidate genes for these and novel deafness loci.