Hi, Linda! You're quite right that traditional sourdough is made without the addition of commercial yeast, but for new sourdough bakers who may not be quite as comfortable with their starter, additional yeast can provide a safety net to help ensure that the bread gets a good rise. In other recipes, yeast can be included to help speed up what might otherwise be a very slow rising process using only starter. But the majority of our sourdough recipes are made the old-fashioned way, with just plain old sourdough starter as the leavener. If you get comfortable with beginner-level sourdough recipes and want to try a naturally leavened recipe like this, our Naturally Leavened Sourdough Bread recipe is a great place to start. Happy baking!

• Reply