Noma is a gangrenous disease that usually begins in the mouth and is characterized by rapid necrotizing destruction of soft tissue and underlying bone. The disease, which is associated with a strong putrid odor suggestive of mixed bacterial infection, develops only in predisposed persons, especially children whose natural defenses have been weakened by poor socio-economic living conditions. However a few atypical cases have recently been reported in adults in whom the main risk factor seemed to be immunodepression. The increasing number of wars in the Third World and the AIDS epidemic raise the likelihood that the number of cases of this disease will rise sharply particularly since the incidence has been grossly underestimated for many years. It now seems clear that a combination of local and systemic risk factors are implicated in the etiopathogenesis of noma with the common denominator being a weakened immune system. This would account for the fulminating course of the infectious process due to one or more opportunistic microbial or cytopathogenic agents or even to a still undetermined immunopathologic reaction that lead to massive tissue destruction. Poor understanding of the etiopathogenesis of noma is a major factor perpetuating the nosologic problems posed by this disease. Some authors add to the confusion by including a range of gangrenous diseases under the heading of noma. It is important that the term noma be applied only to necrotizing processes that begin in the mouth and present the characteristic features and course.