The sociologically study of the Cohabitation in Tehran City

The purpose of this research is the sociologically study of cohabitation phenomenon in Tehran city. In recent years, family institution has experienced many changes which one of them is known cohabitation as a new emerging style of common life. According to nature and subject qualitative research is considered and a purposeful method of sampling and snowball sampling are applied for achieving to theoretical saturation; therefore, in this research 60 person of that experienced cohabitation in 17th Area of Tehran were interviewed. The analyzing of data is based on grounded theory method. The impact factors in the phenomenon of cohabitation can be classified in three categories. The findings show that the following factors have the most impact, including; economic factors (unemployment, lack of job security, costs of marriage) legal factors (the responsibility of marriage, unfair contract between partners and so on) social factors (social changes, generation oppositions, sexual abnormalities and the increasing of conflicts in the society).