Ustilago maydis is the causal agent of the disease known as corn smut or Huitlacohe; their natural hosts are maize (Zea mays L.) and its putative ancestor teocintle (Zea mays ssp. parviglumis and ssp. mexicana). In México there is an evidence of its use as human food since pre-hispanic times. Huitlacoche is a typical Mexican food with interesting nutritional properties and distinctive flavor. Its use in cuisine is considered as a culinary delicacy in Mexico and several parts of the world and the current consumption is increasing markedly, mainly due to its exclusive flavor different from any other known food. Huitlacoche contains proteins, carbohydrates, fats, minerals and vitamins that contribute to its nutritional value, also it has been reported that it contains proteins with balanced levels of essential amino acids, something which does not occur in corn having a deficiency mostly in lysine. The fungus also contains compounds with antioxidant properties, consequently it can be included in what are now known as nutraceutical foods. Besides its use in the food, this fungus has been used in different kinds of basic investigation, such as DNA recombination, signaling, cell biology, biotrophic plant-pathogen interactions and others. Its characteristics of dimorphism, and the detailed knowledge we have on its pathogenic development, that we describe in detail, make it an ideal subject for the analysis of fungal differentiation, and for the knowledge of the behavior of the highly aggressive plant pathogens that are members of its taxonomic group, the Ustilaginales. In the present communication we make a thorough review of the nutritional characteristics of U. maydis, its life cycle, and the molecular bases of its differentiation, morpohogenesis and pathogenicity.