We report the chromosomal localization and a simple sequence repeat (SSR) in the cytosolic phospholipase A₂ (cPLA₂) gene in both human and rat. A (CA)₁₈ repeat in the promoter of the rat gene wasdetermined to exhibit length polymorphism when analyzed using the polymerase chain reaction (PCR) in 19 different inbred rat strains. Genotyping for this marker in 234 F₂ progeny of a SHR × BN intercross mapped the gene to rat chromosome 13. Using a PCR strategy, a fragment of the promoter for the human gene was isolated, and a (CA)₁₈ repeat was identified. Since this marker displayed a low heterozygosity index, we also identified a mononucleotide repeat in the promoter for cPLA₂ that displayed a polymorphism information content value of 0.76. The human gene was mapped using fluorescence in situ hybridization (FISH) to chromosome 1q25. Of interest, the gene encoding the enzyme prostaglandin-endoperoxide synthase 2 (cyclooxygenase-2), which acts on the arachidonic acid product of cPLA₂, was previously localized to this same chromosomal region, raising the possibility of coordinate regulation. Identification of intragenic markers may facilitate studies of polymorphic variants of these genes as candidates for disorders in which perturbations of the eicosanoid cascade may play a role.