The fourth edition now lists approximately 3,200 entries to the literature on wild mammal in Ireland (compared to 2,663 entries in the third, and 1,389 entries in the second edition). A large number of these have come about by re-conection of authors with records of whales, porpoises and dolphins from the Irish Naturalists' Journal Cetacean Notes section. The book is fully indexed and has all relevant websites listed.