Sealworm (Pseudoterranova decipiens species complex), formerly known as codworm, are parasitic nematodes found in the flesh of Atlantic cod (&o;Gadus morhua&o;) and other fish species of commercial importance in the North Atlantic. Detection and removal of these parasites results in production delays and degradation of products, and is costly for the fish processing industry. This book results from a NAMMCO Working Group, established to address this issue convened in Tromso, from 10 to 14 March 1997, and was attended by scientific experts from Canada, the U.K., Iceland and Norway.