The Denkard is a 'theological compendium', written in the 9th century A.D. by some compilers using ancient data from the Sassanian period (3th-7th century A.D.). This work is divided into nine books, but the two first are lost. The third one was translated in French by J. de Menasce (Paris, 1973), and the sixth in English by S. Shaked (Boulder CO, 1979). The fifth book published here for the first time is a critical edition by the late A. Tafazzoli, who tragically passed away in 1997, and by professor J. Amouzgar who had to finish the work alone. Less philosophical than the book III, this book V is nevertheless a mine of informations on Mazdean cosmogony, legends on Zoroaster, eschatology, ritual and purity laws, etc. in the literary form of 'Questions and Answers'. Jaleh Amouzgar s'est formee a Teheran et a Paris (doctorat-es-lettres sous la direction de J. de Menasce, 1968). Chercheur a la Bonyad-e Farhang-e Iran (1968-1969), puis professeur a l'Universite de Teheran depuis 1970. Ahmad Tafazzoli (1937-1997), forme a Teheran, Londres et Paris, s'est rapidement impose par ses travaux comme le meilleur specialiste de l'Iran ancien dans son pays. Il est Professeur a l'Universite de Teheran a partir de 1970 et Vice-president de l'Academie Iranienne de langue et litterature persane.