The concentrations of platelet-activating factor (PAF), leukotriene-B4 (LTB4), and tumour necrosis factor-alpha (TNF-alpha) in homogenate supernatants of gastric mucosal biopsy specimens and in gastric juice from Helicobacter pylori-positive (N = 21) and -negative children (N = 14) were investigated in order to determine whether these lipid mediators and the cytokine are involved in the inflammatory reaction of H. pylori-associated gastritis. PAF and LTB4 concentrations were measured after high-performance liquid chromatography (HPLC) purification by specific radioimmunoassay, and TNF-alpha concentrations were determined by using an enzyme-linked immunosorbent assay. The concentrations of PAF, LTB4, and TNF-alpha measured in gastric juice and biopsy homogenate supernatants of children with H. pylori-positive gastritis were found to be statistically elevated and in positive correlation with each other. This study suggested that increased local mucosal production of potent proinflammatory agents such as PAF, LTB4, and TNF-alpha may be implicated in the pathogenesis of H. pylori-associated gastritis in childhood.