The sensory cells of the ear, the hair cells, are damaged by loud noise or certain types of drugs. In the bird cochlea, new hair cells are produced to replace those that are lost. Regeneration also occurs in the vestibular epithelia of birds, fish, and mammals but does not occur in the mammalian cochlea. In order to further our understanding of the regeneration process in the bird cochlea, we have begun to identify the genes that are involved. However, the small size of this organ has made it difficult to use traditional molecular biology methods to address these problems. Recently, many molecular techniques have been adapted for use with small amounts of tissue. Northern blot analysis, the ribonuclease protection assay, semiquantitative PCR and differential display of mRNA are all techniques that are being used to greatly improve our understanding of hair cell regeneration and may eventually provide the information necessary to induce regeneration in hearing-impaired humans.