This multi-authored publication presents illustrated keys to the 19 families and 706 described genera of Chalcidoidea known to occur in the Nearctic region. There are approximately 330 differences between the genera keyed and those listed in the most recent (1979) North American catalog, including about 200 additional genera. The book consists of 22 chapters by 17 world experts, plus an appendix of about 130 generic names no longer considered valid for the region, and separate indexes to chalcidoid names, animal hosts, and plant hosts. The first three chapters provide an introduction, review of chalcidoid structure, and an overview of the superfamily, including a 40 couplet key to families. Each of the remaining 19 chapters reviews one family and includes introductory sections on its recognition, systematics and relationships, biology, literature, an annotated key to the Nearctic genera, and for larger families an index to genera based on couplet number. Over 1800 line drawings and scanning electron micrographs illustrate the keys. The annotations include references to existing keys to species, estimated number of species, and known distribution and host range in the region.