As a response to urban decline and deterioration in cities, especially over the past 50 years, government policies and programs have been developed to confront this problem. This event has occurred not only in developed countries but also developing countries such as Iran. Urban decline has been studied in different dimensions: physical, economical, environmental and social. Also studies have focused on defining urban blight indicators. Review of literature also shows that studies have focused on defining causes of urban blight and solutions to urban blight. This research takes the first step which is a spatial analysis of urban blight, to define urban physical blight in Tehran city. Geographic Information System was used to define Tehran physical blight. Three criteria: High percentage of non-durable buildings in a block, high percentage of small houses (less than 100 square meter land area) and high percentage of alleys with less than 6 meters width were used to define obsolete fabric. The results of analysis show that Tehran's city physical growth follows Burgess Model or Concentric Zone Model. It means that city has expanded from a core (from inner zone) toward the edges (outer zone). Also, the result of study shows that obsolete fabrics are located in the core of Tehran city wherethe origin of the city, which is the oldest fabric is located. Tehran's Old bazaar is also located in the core. Around the core zone, a transitional zone is developed where the old residential units are converted into bazaar's warehouses.
