To confirm the biological effects of peptide growth factors on auditory neuron (AN) in vitro, the influence of NFG and bFGF on the survival status and the neurite regrowth of dissociated primary AN in postnatal chicks was studied with serum-free culture technique and cytologic quantitative method. The results demonstrated that the growth of non-neuron elements such as Schwann's cell was predominant in the earlier stage of culture. The neurite regrowth (bipolarity or unipolarity) of AN was observed at 24 hours after seeding. The growth rate increase during 48-72 hours in the surviving AN. These findings indicated that both growth factors exerted direct neuronotrophic effect on dissociated AN in vitro. NGF and bFGF acted in cooperation to promote the axon regeneration of AN. The concentration-dependent effect of NGF on neurite regrowth and neurone survival was found in the present study. The biological mechanism of NGF and bFGF on AN in vitro has been discussed.