Tehran, the capital city of Iran and a metropolis with a population of 8.2 million and containing 2.4 million households, generated 2,626,519 tons of solid waste in 2005. The present study is aimed at evaluating the generation, characteristics and management of solid waste in Tehran. Municipal solid waste comprises more than 97% of Tehran's solid waste, while three other types of solid waste comprise less than 3% of it, namely hospital waste (1.0%), industrial waste (0.6%) and construction and demolition waste (0.5%). The contribution of household solid waste to total municipal solid waste is about 62.5%. The municipality of Tehran is responsible for the solid waste management of the city; the waste is mainly landfilled in three centers in Tehran, with a small part of it usually recycled or processed as compost. However, an informal sector is also active in collecting recyclable materials from solid waste. The municipality has recently initiated some activities to mechanize solid waste management and reduce waste generation. There remain important challenges in solid waste management in Tehran which include: the proper collection and management of hospital waste; public education aimed at reducing and separating household waste and educating municipal workers in order to optimize the waste collection system; and the participation of other related organizations and the private sector in solid waste management.