Modifications of mucosal phospholipids have been detected in samples from patients with Helicobacter pylori-positive gastritis. These alterations appear secondary to increased phospholipase A₂ activity (PLA₂). The cytosolic form of this enzyme (cPLA₂), normally involved in cellular signaling and growth, has been implicated in cancer pathogenesis. The aim of this study was to investigate cPLA₂ expression and PLA₂ activity in the gastric mucosae of patients with and without H. pylori infection. In gastric biopsies from 10 H. pylori-positive patients, cPLA₂ levels, levels of mRNA as determined by reverse transcriptase PCR, levels of protein as determined by immunohistochemistry, and total PLA₂ activity were higher than in 10 H. pylori-negative gastritis patients. To clarify whether H. pylori had a direct effect on the cellular expression of cPLA₂, we studied cPLA₂ expression in vitro with different human epithelial cell lines, one from a patient with larynx carcinoma (i.e., HEp-2 cells) and two from patients with gastric adenocarcinoma (i.e., AGS and MKN 28 cells), incubated with different H. pylori strains. The levels of cPLA₂, mRNA, and protein expression were unchanged in Hep-2 cells independently of cellular adhesion or invasion of the bacteria. Moreover, no change in cPLA₂ protein expression was observed in AGS or MKN 28 cells treated with wild-type H. pylori. In conclusion, our study shows increased cPLA₂ expression and PLA₂ activity in the gastric mucosae of patients with H. pylori infection and no change in epithelial cell lines exposed to H. pylori.