Abstract Mannitol is a polyol or sugar alcohol that is produced by several organisms. Mannitol is assumed to have several beneficial effects, as an antioxidant (protection against oxidative damage by oxygen radicals) and as a non-metabolizable sweetener. Mannitol can therefore be applied to foods leading to health-promoting effects (functional foods). Mannitol-producing lactic acid bacteria may directly be applied in the manufacture of foods and this may lead to fermented food products with an extra nutritional value. In this article, the production of mannitol by lactic acid bacteria is reviewed. Several heterofermentative lactic acid bacteria produce mannitol in large amounts, using fructose as an electron acceptor, whereas homofermentative lactic acid bacteria only produce small amounts of mannitol, often only when the bacteria are defective in lactate dehydrogenase activity. The physiology, pathways and genetics of mannitol production in both homofermentative and heterofermentative lactic acid bacteria are presented and discussed.