Many eukaryotic proteins are bound to the plasma membrane via a glycosylphosphatidylinositol (GPI) anchor. Its core backbone, which is conserved in different organisms, is synthesized in the endoplasmic reticulum by the sequential addition of glycan components to phosphatidylinositol. One of the human GPI synthesis genes, PIGF (phosphatidylinositol glycan complementation class F), which is involved late in the synthesis pathway, has been cloned. In this study, we isolated complementary and genomic clones of Pigf, a murine counterpart of PIGF. Pigf encodes a 219 amino acid protein that complements a class F mutation. The Pigf gene consists of six exons spanning 30 kb and was mapped to chromosome 17 at 17E4-E5. These features are very similar to PIGF, thus demonstrating the interspecies conservation of structure, function, gene organization, and genetic locus between these GPI synthesis genes. The results also extend a region in murine distal chromosome 17 that is syntenic to human chromosome 2p16-p22.