Some protozoan parasites encode iron superoxide dismutase (FeSOD), but mammalians do not, and FeSOD is therefore an attractive target for drug therapy. Database screening revealed that the social amoeba Dictyostelium discoideum encodes a protein similar to FeSOD. Since D. discoideum is non-pathogenic and easy to main-tain in laboratory conditions, analysis of the protein would contribute to drug design and chemotherapy for infectious diseases. RT-PCR analysis showed that the gene for the protein was expressed at a high level in growing cells and at decreased levels in subsequent developmental stages. Fluorescence of green fluorescent protein fused with the N-terminal region (Met1 - Leu35) of the D. discoideum protein was detected in mitochondria, indicating that the protein is localized in mitochondria.