A large number of organic acids with actual or potential uses are produced by microorganisms. Citric, itaconic, lactic, malic, tartaric, gluconic, mevalonic, salicyclic, gibberelic, diamino-pimelic, and propionic acids are some of the acids whose microbial production have been patented. Citric acid is used in the food industry, in medicine and pharmacy, in the cosmetic industry and other industries. Citric acid is the major food acidulant used in the manufacture of jellies, jams, sweets, and soft drinks. Sodium citrate is used in blood transfusion for the prevention of blood clotting. It is used in astringent lotions such as aftershave lotions because of its low pH. This chapter presents uses of citric acid, biochemical basis of the production of citric acid, fermentation for citric acid production and extraction of lactic acid. The chapter also presents uses of lactic acid, properties and chemical reactions of lactic acid, fermentation for lactic acid production and extraction of lactic acid from fermentation medium.