Not long to go ...
Coming from Madrid take the A-2 (main road) as far as Medinaceli: Change to the N-111 for Soria: Then take the N-122 as far as Tudela, and from there you can choose between taking either the N-121, or the motorway AP-15, straight to Pamplona. The motorway has a toll and it costs +8 € for the 83 klm. stretch. The whole journey from Madrid to Pamplona takes about four hours. (About 400 klms.)
Coming from Barcelona: the easiest route is to take the Motorway AP-2 as far as Zaragoza (Alfajarín), then the Motorway AP-68 to connection with AP-15 and then switching to the AP-15 straight to Pamplona. There is a toll and the total price from Barcelona is +36 €. If you come from Lleida it is a little bit cheaper: +25 €.
If you come from Europe by car the most convenient place to cross into the Spanish State is from IRUN. However, if you want to do some sightseeing along the way, there are more picturesque mountain crossings at Ibardin, Dantxarinea, Valcarlos or Eugi. Coming from IRUN the shortest and best route is the N-121 over the Belate pass. However, if you are in a big hurry, then go to San Sebastian and take the motorway A-15. (There is a short toll stretch between Irurzun and Pamplona of about 20 kms. which costs about +2 €). This is a fast and comfortable route which takes about one hour. If you go by Belate, it takes about one and a half hours.