Yeasts have been utilized by man since ancient times-specifically, when he first learnt that fruit juices developed into intoxicating drinks and that the dough produced from his ground cereal can be leavened. Today, yeasts which are produced and used in all six continents of the world form the single most produced microorganism in terms of weight. For example, in the US alone, baker’s yeast is manufactured by at least six major companies. These companies are Universal Foods (Red Star Yeast), Fleischmann’s, Gist-brocades, Lallemand (American Yeast), Minn-dak, and Columbia. The production of baker’s yeasts has received the greatest attention followed by food and fodder yeasts. Due to recent interest in the production of single cell protein, food and fodder yeasts may become as important as baker’s yeasts in terms of total quantity produced. This chapter discusses production of baker’s yeast with emphasis on yeast strain used, culture maintenance, factory production, food yeasts, production of food yeast, feed yeasts, alcohol yeasts and yeast products.