The rites and mysteries of Eleusis were kept strictly secret and an initiate could reveal nothing of the celebration of Demeter -- on pain of exile or even death. This secrecy was supported and enforced by the Athenian State. Though the cult of Demeter operated in Eleusis for over 2,000 years with annual celebrations and countless initiates, this veil of secrecy still lies upon those ancient mysteries. Portions of the initiation were held in public and the record of these rites has been preserved, but the true mysteries of Demeter will remain secret forever.

The cult of Demeter, of course, focused mainly upon Demeter herself as well as her daughter Persephone (Kore). Hades (Pluto) also shared a part of the cult's attention. The gods Iacchos and Triptolemos were also honored at Eleusis, but do not seem to be essential to the secret rites of the cult.

The chief priest of the cult of Demeter was called the Hierophant. Chosen from the Eumolpid family for this life time office, the Hierophant revealed the Hiera to the initiates and was the only person allowed into the Anaktoron of the temple. His personal assistants were the Hierophantides. Additionally, there were many other clergy, including: the priestess of Demeter (nearly as revered and influential as the Hierophant), the priestesses panageis (women whose role is now unknown), the Dadouchos (purifier of initiates and torch bearer), the Hierokeryx (the herald), and various other lesser priests. Nearly all of these positions were held by members of either the Eumolpid or Kerykes families. In this way, the event of Eumolpos being the first initiate and the one who first taught the mysteries to others was reinacted by one of his descendents for the next 2,000 years.