Objectives: The study was meant to measure the prevalence of mental disorders among the people of Valian, a village in Tehran province, who aged 15 and over. Method: All the residents of Valian village aged 15 and over(N=630) were studied through General Health Questionnaire (GHQ-28) and clinical interviews based on DSM-IV. Findings: The prevalence rate of mental disorders measured 26.5%,(35.7% and 14.6% for females and males respectively). Highly common mental disorders were free-floating anxiety(11.7%),major depression(11.3%),simple phobia(7.3%), dysthymia (5.6%), and obsessive-compulsive disorder(4.3%). Mental disorders proved to be more prevalent among females, illiterate and low-literate individuals over 45 years of age, and among families with traces of mental disorders or with kinship between parents. No significant relation was found between “marital status”, “birth hierarchy” and mental disorders. However, prevalence of mental disorders among working women measured less than that among housewives. Some 35.5% of subjects claimed to have referred, some time in the past, to a physician/psychiatrist for the mental disorder they were suffering from, though none received appropriate, regular and continuous treatment and or sufficient doses of medication. The study demonstrated that, out of the total number of the patients only 3.6% were covered by the National Programme of Mental Health in the village. However all the psychotic patients identified were covered by the programme.