Interferon-gamma (IFN-gamma)-like-immunoreactivity was observed in subsets of rat skeletal muscle fibres with 3 different mouse monoclonal antibodies directed to rat IFN-gamma and a rabbit polyclonal anti-rat IFN-gamma-antibody. These strongly IFN-gamma-immunoreactive fibres also expressed antigen defining T-cells of the cytotoxic/suppressor phenotype (CD8) and major histocompatibility complex (MHC) class I antigen.