The aim of the present study was to localize the neurotrophic factors glial cell line-derived neurotrophic factor (GDNF), nerve growth factor receptor (NGFr) and low sensitive receptor for NGF (p75LNGFR) in rat testes during the postnatal development. Rat testes obtained at different stages of the postnatal development--day 5, 10, 15, 20, 24 and 27 after birth were used. Amplification immunocytochemical technique, which includes a combination of the peroxidase-antiperoxidase method (PAP) and the avidin-biotin peroxidase complex (ABC) methods, was applied. Immunoreactivity for the tested antigens was established in the Leydig cell with characteristic fluctuation in the intensity of the immune reaction at the different stages of the postnatal development. Positive immunostaining was seen in the Sertoli and some of the germ cells (spermatocytes and spermatids). The results obtained show that neurotrophic factors play a role in the processes of postnatal differentiation of the Leydig cells and in the regulation of their functional activity.