This volume is a republication in one volume of the 10 part CIH Keys to the Nematode Parasites of Vertebrates, first published between 1974 and 1983. For many years the 'Keys' have provided a working tool to those within the field and laboratory needing to know 'what is this worm?'. Now due to popular demand and to coincide with the long awaited publication of the supplement volume, the 'Keys' will be presented as one volume, refreshed and reformatted with the additional convenience of reordering in to superfamily. As an indispensable guide the 'Keys' shall continue to be an essential resource to those working within medical, veterinary and biological departments worldwide for many more years to come.