From December 11, 2002 properly documented dogs and cats from the U.S. and Canada can enter the U.K. under the U.K. Pet Travel Scheme (PETS) without spending any time in quarantine. The process requires several detailed steps (in this order): your pet must be microchipped, vaccinated against rabies and then receive a blood test from a U.S. veterinarian. After reviewing the above paperwork, a USDA-authorized veterinarian can supply the official PETS certificate needed to bring your dog or cat into the U.K.. With the proper paperwork in hand, and a final treatment against ticks and tapeworms shortly before travel, your pet can enter the U.K. together without a quarantine requirement!

For a fact sheet and more information, visit the PETS website at http://www.defra.gov.uk/animalh/quarantine/index.htm or call the PETS Helpline on 011-44-870-241-1710 (Monday to Friday - 08.30-17.00 U.K. time). 

*snort*