BACKGROUND We have studied the cytokine production patterns in gastric mucosal biopsy specimens with and without the Helicobacter pylori infection, using a reverse transcription-polymerase chain reaction (RT-PCR) method capable of detecting low levels of specific mRNA. METHODS Total RNA was prepared from biopsy specimens with the acid guanidinium thiocyanate-phenol-chloroform method. cDNA was synthesized by M-MLV RTase and amplified using the oligonucleotide primers specific for interleukin-1 beta (IL-1beta), IL-2, IL-3, IL-4, IL-5, IL-6, IL-7, IL-8, IL-9, IL-10, tumor necrosis factor-alpha (TNF-alpha), interferon-alpha (IFN-alpha), IFN-beta, and IFN-gamma by PCR methods. RESULTS Although IL-1 beta and IFN-gamma mRNA were detected in most specimens, IL-2, IL-3, IL-4, IL-5, IL-9, TNF-alpha, and IFN-beta mRNA were not detected at all. The expressions of IL-7 and IL-8 mRNA were significantly higher in H. pylori-positive gastritis than in H. pylori-negative normal controls. There was a significant correlation between the expression of IL-8 mRNA and the severity of gastritis both in the antrum and in the corpus. On the other hand, there was a significant correlation between the expression of IL-7 mRNA and the severity of gastritis only in the corpus. CONCLUSIONS These findings suggest that some cytokines, especially IL-7 and IL-8, play some roles in H. pylori-associated gastritis.