- EU Pet Passport (for pets arriving from EU countries). In order for the EU Pet Passport to be issued, the pet must be micro-chipped and vaccinated against rabies.
- Proof of rabies vaccination within 15 days prior to date of arrival if coming from a non-EU country.
- International Certificate of Health from an accredited veterinarian (in the US known as USDA Form 7001) if coming from a non-EU country.
- Micro-chipping details if coming from a non-EU country.
- Fitness To Fly certificate if arriving by air (required by most airlines).

Added March 2007 by Kerstin:
Readers might be interested in knowing that some dogs, classed as "potentially dangerous" need a special licence.

We're thinking about moving to Portugal and have found out that like Spain, we have to complete a lot, no seriously, a lot of paperwork! So different from Ireland where we bought a licence from the post office!

FYI Law is quoted on this site:
http://www.sosanimal.com/html/body_dec312-2003.html

http://www.rcp.pt/index.php?n=34&a=59