The deal will see the race known as the Sharpie 500 until 2008.
The announcement comes just two days before the running of the Sharpie 500 this weekend - the third-year of the sponsorship.
Said Bob Parker, president of the Sharpie Group: "Our commitment to Bristol and the millions of race fans across the country and around the world means more than just a sponsorship extension.
"We're pleased to be taking the relationship to a new level."
Sharpie is also a major sponsor of the No. 97 Rubbermaid/Sharpie Ford and Kurt Busch, currently eighth in the 2003 Winston Cup points race.
