IntroductionThe trace elements selenium is a constituent of the antioxidant enzyme glutathione peroxidase. Becauseit boosts the body’s antioxidant capacity, selenium is thought to have some ability to control cell damagethat may lead to cancer. Selenium low status has been linked to increased risk of various diseases, suchas cancer and heart disease.GoalInvestigate serum selenium level of adult mongolians and conduct age and gender coparartive analysisof the serum selenium content.Materials and MethodsCross sectional study was performed among the 2339 apparently healthy Mongolians of both gendersaged ≥18 years. In the study were used questionnaire and biochemical methods. Blood samples werecollected from all subjects and serum selenium concentration was measured by atomic absorptionspectrophotometry method using thermo fisher scientific analyzer.ResultsThe mean and confidence interval of serum selenium level in adult Mongolians was 0.78 μmol/l (95%CI0.77-0.79) and there was no significant difference between genders. Thus the mean was 0.77 μmol/l(95%CI 0.76-0.80) among women and in men it was 0.78 μmol/l (95%CI 0.76-0.80). Data analysisrevealed that older age group individuals were at risk of lowered serum selenium level. In particular,the oldest age group of over 60 years (females: 0.74 μmol/l, 95%CI 0.70-0.77; males: 0.68 μmol/l,95%CI 0.64-0.71). The difference in selenium status between age groups was statistically significant inboth sexes. The overall prevalence of serum selenium concentrations indicative risk of deficiency was59.7%, with no significant differences in the prevalence by genders. Survey findings revealed that riskof selenium deficiency had statistically significant difference between age groups among the surveyedmen.Conclusion: The mean value of serum selenium in adult Mongolians was 0.78 μmol/l and there was nosignificant difference between genders.