Helicobacter pylori, a gram-negative spiral bacterium, has been associated with chronic gastritis and gastric cancer. HP 99, isolated from the Korean patients, and NCTC 11637, obtained from ATCC, have different genotypes. The present study aims to investigate whether these H. pylori strains show the discrepancy for activating transcription factors (NF-kappaB, AP-1, C/EBP) and induction of cyclooxygenase-2 (COX-2) gene in gastric epithelial AGS cells. After treatment of H. pylori to AGS cells at the ratio of 300:1, the activation of transcription factors was assessed by electrophoretic mobility shift assay. COX-2 protein was determined by Western blot analysis. The level of 6-keto-prostaglandin F(1alpha) (6-keto-PGF(1alpha)), a COX-2 product, was measured in the medium by enzyme-linked immunosorbent assay. As a result, both H. pylori strains similarly induced COX-2 expression via activation of NF-kappaB, not C/EBP, and increased the level of 6-keto-PGF(1alpha). HP 99 showed much higher activation of AP-1 compared to NCTC 11637. NF-kappaB might play an important role in COX-2 expression in H. pylori-induced gastric inflammation as compared to other transcription factors.