To understanding the serological status of H9N2 avian influenza virus in human population according to age bias, we studied 240 serum samples from male persons with ages between 5-70 years of age in different regions of Fars province, Iran. Haemagglutination-Inhibition assay was used for evaluation of H9N2 antibody titers in persons sera. None of these persons received any of influenza A vaccines. All persons clinically normal without any influenza-like illness and were encouraged to participate in this study by veterinary information agency. Age distribution was as follows: 5-15 years, 8.0%; 16-26 years, 12.0%; 27-37 years, 16.0%; 38-48 years, 20.0%; 49-59 years, 22.0%; and 60-70 years, 22.0%. The increasing seropositive rate with increased years of age could be due to frequent exposures during the life periods.