The purpose of the present study was to investigate the mental health of adolescents and young people in Tehran. The sample included 464 girls and boys from age 15-30 years. The GHQ-28 scale designed by Goldberg and Hiller (1979) used for screening the mental illness people from normal ones. This test composed of 4 subscales: anxiety disorder, somatoform disorder, social dysfunction and depression disorder. The result of this study indicates that 29.3 percent of people have mental illness, and there is a significant difference between males and Females and between single people and married people. Also there is a correlation between age and mental health and the most prevalence disorder is social dysfunction.