In order to determine the prevalence of depression among high school students of Tehran, the Beck depression test questionnaire was distributed among 1478 students of Tehran 19 districts, using a methodical approach. Data gathered after completion of the forms showed the following results: 11.4% of the students were on the border line of affliction, 12.6% had a medium degree of disorder, 4.2% suffered from a severe level and 0.4% showed a much higher degree of depression. The older these students were, the more prevalent was the depression among them. The girls showed a higher degree of disorder than the boys at a 1.4 to 1 ratio. The lowest degree was found among students of mathematics, whereas the students of literature showed the highest level. The rate was much lower among students of Shahed schools than that observed among students of evening classes. The research showed no relationship between the students depression and their parents profession. However, the higher level of parents' education was associated with lower levels of depression among their children. Finally, lower levels of disorder was observed among residents of private housings in comparison to what was found among students residing in leased or mortgaged dwellings