Abstract: The blow fly (Calliphoridae) and flesh fly (Sarcophagidae) (Diptera: Cyclorrhpha) are flies of great ecological, medical and sanitary importance because they are decomposers of organic matter, mechanical vectors of pathogenic agents and causers of myiasis. This study was conducted to ascertain the fauna of Sarcophagidae and Calliphoridae in Tehran and suburb, over the period of three years during 1996-97 and 2000-2002, with ten monthly collections, continuously. Adult flies were netted and collected in different areas, indoors and outdoors and taken to the laboratory for identification. Twenty-two species of flies were identified. Thirteen species were medically important and four species consisting: Calliphora vomitoria, Lucilia richardsi, Sarcophaga fertoni and Sarcophaga peregrina were identified and reported for the first time in Iran.