Nerve growth factor receptor (NGFR) mRNA expression was examined in the developing rat cerebellum with in situ hybridization histochemistry. The probe used in this study was the 57-mer oligonucleotide complementary to the rat NGFR cDNA (bases 798-855). The specificity of the hybridization was determined with a 'sense' probe. From the age of postnatal day 0 (PND 0), hybridization signals were detected in the external granule cell layer, Purkinje cell layer, and meningeal cells of the cerebellum. Until PND 10, the external granular cell layer consistently expressed high levels of NGFR message, with the densest hybridization signal observed in the proliferative zone. NGFR mRNA level in this layer rapidly decreased at later ages and was barely detectable after PND 16. In the Purkinje cell layer beyond PND 4, the hybridization signal became more intense, reached a peak level around PND 10, and then gradually decreased. NGFR mRNA was detected until PND 30 in this layer. Meningeal cells expressed NGFR message from PND 0 to PND 8. These results suggest that NGF may be involved in cerebellar development as a mediator of morphogenesis and/or synaptogenesis.