English translation of the original guide to Palaearctic Encyrtidae (Hymenoptera: Chalcidoidea) published in Russian by V.A. Trjapitzin in 1989. The book summarizes information on this economically important group of parasitoids occurring in the Palaearctic zoogeographic region. The first part includes information on the morphology, host relationships, economic importance, distribution and classification of Encyrtidae. The second part includes keys to aid in the the identification of all 211 genera and 1260 species known from the region. It is an essential work for all those interested in Chalcidoidea and especially Encyrtidae.