An acoustic trauma model for study of the repair of the auditory epithelia was established in postnatal 8-14 days chicks. The animals were continuously exposed to the wide band noise at 115 dB (A) for 72 hours. The tracer of DNA replication-[3H] thymidine (3H-dR) was given in vivo or in vitro during or after exposure. The basilar papilla were cultured and processed with autoradiographic technique. The results demonstrated that at 48 hours following initial labelling of tracer, the incorporation of 3H-TdR was found over the nucli of supporting cells (or precursor cells) in the injured region of basilar papilla. The labelled hair cells appeared at 96 hours near the labelled supporting cells. Until the fifth to sixth days of culturing, the regenerated hair cells were still immature morphologically. No sign of labelled hair cells were detected in the control animals. Our findings indicated the potential capability of cellular proliferation and DNA replication in damaged auditory epithelia in vitro. Some kind of supporting cells in damaged region could be the precursors for regenerating hair cells. The positive cells labelled with 3H-TdR migrated to the surface of basilar papilar and differentiated into hair cells eventually. Therefore, it could be speculated that a homogeneous relationship may exist between labelled supporting cells and labelled hair cells.