The primary ingredient in Eastern North Carolina barbecue sauce is vinegar.
Eastern-style sauce is typically thin and vinegar-and-pepper based, with no tomato. Its sharp acidity seasons whole-hog barbecue and helps cut through the richness of slow-cooked pork. Salt, black pepper, red pepper flakes, and other spices may be added, but vinegar provides the defining base.
Eastern North Carolina barbecue traditionally uses the entire hog rather than only the shoulder. The meat is cooked slowly over hardwood coals, then pulled from the bone and chopped. The thin sauce may be brushed on during cooking or added afterward, where it works as both seasoning and finishing sauce.
The most common mix-up is Lexington, or Western North Carolina, style. Lexington sauce also uses vinegar, but typically includes tomatoes or ketchup and is served with pork shoulder. That difference reflects a broader regional barbecue divide: Eastern style is whole-hog and tomato-free, while Lexington style is shoulder-based and often sweeter and redder. Both styles are historically important in North Carolina, so “North Carolina sauce” alone can be too broad without specifying the region.