The temple of Hephaistos is located on the hill of the Agoraios Kolonos on the west side of the Ancient Agora of Athens. This temple which previously was called “Theseion”, was built about the middle of the 5th century B.C. It is one of the best preserved monuments. The present work includes the study of the history of the temple and the pervious attempts to preserve it. According to bibliography and personal observation the existing erosion of the temple has been recorded and an environmental study on the site of the Ancient Agora has been made. Based on the above facts a general study about the conservation of the temple has been made.