On every continent and in every nation, animals unrecognized by modern science are reported on a daily basis. People passionately pursue these creatures--the name given to their field of study is cryptozoology. Coined in the 1950s, the term literally means the science of hidden animals. When the International Society of Cryptozoology (ISC) was formed in 1982, the founders declared that the branch of science is also concerned with "the possible existence of known animals in areas where they are not supposed to occur (either now or in the past) as well as the unknown persistence of presumed extinct animals to the present time or to the recent past...what makes an animal of interest to cryptology is that it is unexpected."

This reference work presents a "flesh and blood" view of cryptozoology. Here, 2,744 entries are listed, the majority of which each describe one specific creature or type of creature. Other entries cover 742 places where unnamed cryptids are said to appear; profiles of 77 groups and 112 individuals who have contributed to the field; descriptions of objects and events important to the subject; and essays on cryptotourism and hoaxes, for example. Appendices offer a timeline of zoological discoveries, annotated lists of movies and television series with cryptozoological themes, a list of crypto-fiction titles and a list of Internet websites devoted to cryptozoology.