The cDNA for goose interferon gamma (goIFN-γ) was cloned from PHA-stimulated goose peripheral blood mononuclear cells (PBMCs) by RT-PCR. This cDNA encodes a 19-amino acid signal peptide and a 145-amino acid mature protein, which shares a high homology with duck IFN-γ. Recombinant mature goose interferon gamma (rgoIFN-γ) generated from both prokaryotic and eukaryotic expression systems effectively inhibited the replication of goose paramyxovirus and recombinant vesicular stomatitis virus in vitro. These antiviral activities were abrogated by rabbit anti-rgoIFN-γ antibodies in vitro. Furthermore, rgoIFN-γ stimulated goose peritoneal macrophages to produce nitric oxide (NO) in vitro, demonstrating its macrophage activating factor (MAF) activity. Therefore, the availability of bioactive rgoIFN-γ and its specific antibodies provides valuable tools for studying T cell immunity in geese