Background & Objectives: Matrix Metalloproteinases (MMPs), a member of photolytic enzyme family, degrade the extra cellular matrix. MMPs have very important roles in physiological and pathological processes. It has been reported that MMPs concentration increase in malignancies such as stomach, breast, colon, lung, head and neck cancers . Infection with Helicobacter pylori is risk factor for gastric cancer and may increase the serum level of MMP-9. The aim of this study was to measure the concentration of MMP-9 in sera of patients infected with H. pylori.

 Methods: In a descriptive-experimental study, apparent healthy individuals who were refereed for stool and blood tests were randomly selected and their stools and sera samples were collected. A questionnaire containing age, sex, smoking and special diseases in family and type of their diseases was filled for every volunteer. The sera collected immediately after blood sampling and stored in -70^oC until used. The concentration of MMP-9 was assessed using ELISA. Stool samples were used for detection of H. pylori antigen.

 Results: H. pylori positive, negative and equivocal volunteers were 52.38%, 29.76% and 17.85%, respectively. Differences between MMP-9 concentration and H. pylori negative and positive groups were not significant (p=0.25). A significant increase in MMP-9 concentration was found in sera from drivers in compare with housewives.

 Conclusion: Although there was an increase in serum concentration of MMP-9 in H. pylori infected person, differences between H. pylori negative and positive groups were not significant. The raised concentration of MMP-9 in drivers may arise from difference in their health condition in compare with the housewives. This study suggests that MMP-9 level in serum may increase before initiation of gastric cancer in H. pylori infected individuals.