We purified a phospholipase A2 (PLA2) from human ileal mucosa to homogeneity. Its NH2-terminal amino acid sequence, amino acid composition, molecular weight, and elution behavior on reverse phase high-performance liquid chromatography were identical to those of human group II PLA2 purified from synovial fluid or spleen. The ileal PLA2 preferred anionic phosphatidylglycerol as substrate. On immunoblot analysis, human ileal mucosa gave more intense immunoreactivity with anti-human synovial fluid PLA2 antibody, at the same position as the purified enzyme, than the cecal mucosa. Northern blot analysis also showed that the level of group II PLA2 mRNA in the ileal mucosa was greater than that in the cecal mucosa. The enzyme was rather uniformly distributed over the colonic mucosa, from cecum to sigmoid colon. These results indicate that the ileal mucosa contains group II PLA2, and that its expression in the ileal mucosa was higher than that in the colonic mucosa.