Characterization of lymphokine-activated genes in mouse macrophages led to the identification previously of Mumig, an interferon-gamma-inducible murine gene that encodes a member of the chemokine family of cytokines. The Mumig cDNA probe was used to screen a cDNA library prepared from cultures of the THP-1 human monocytic cell line that had been treated with interferon-gamma. This led to the identification of Humig, a new human member of the chemokine gene family. Humig is induced in THP-1 cells and in peripheral blood mononuclear cells by interferon-gamma but not by interferon-alpha or by lipopolysaccharide. Analysis of mouse and human genomic DNAs suggested that the Mumig and Humig genes are true mouse-human homologues. The Humig mRNA encodes a predicted secreted HuMig protein of 103 residues, M(r) 11,725.