US-based National Hot Dog & Sausage Council found mustard to be the most popular

Hot dogs are commonly served with one or more condiments. In 2005, the US-based National Hot Dog & Sausage Council (part of the American Meat Institute) found mustard to be the most popular, preferred by 32% of respondents; 23% favored ketchup; 17% chili; 9% pickle relish, and 7% onions. Other toppings include sauerkraut, mayonnaise, lettuce, tomato, cheese, and chili peppers. Condiment preferences vary across the U.S.. Southerners showed the strongest preference for chili, while Midwesterners showed the greatest affinity for ketchup.