The expression of major histocompatibility complex (MHC) class I molecules on adult mouse DRG neurones was analysed using immunofluorescence and reverse transcription-polymerase chain reaction (RT-PCR). MHC class I molecules were not expressed in untreated dorsal root ganglion (DRG) neurones. The molecules, however, were detected on the surface of neurones following IFN-gamma treatment. In addition, expression of the MHC class I beta 2-microglobulin and genes was induced in neurones following IFN-gamma treatment. Expression of Tap-1 and Lmp-2 genes, which are involved in antigen processing and presentation, was also induced by IFN-gamma treatment. These results indicated that DRG neurones are able to express MHC class I molecules following IFN-gamma treatment and suggest that DRG neurones themselves are susceptible to recognition by cytotoxic T cells.