MUDENG (mu-2-related death-inducing gene, MuD) encodes a predicted ∼54-kDa protein in humans, considered to be involved in trafficking proteins from endosomes toward other membranous compartments as well as in inducing cell death. Here we report on the generation of a mouse monoclonal antibody (MAb) against the middle domain of human (h) MuD. This IgG sub 1 MAb, named M3H9, recognizes residues 244-326 in the middle domain of the MuD protein. Thus, the MuD proteins expressed in an astroglioma cell line and primary astrocytes can be detected by the M3H9 MAb. We showed that M3H9 MAb can be useful in enzyme-linked immunosorbent assay (ELISA) and immunoblot experiments. In addition, M3H9 MAb can detect the expression of the MuD protein in formalin-fixed, paraffin-embedded mouse ovary and uterus tissues. These results indicate that the MuD MAb M3H9 could be useful as a new biomarker of hereditary spastic paraplegia and other related diseases.