The information presented is based on (1) informal interviews with law enforcement officials; (2) an analysis of the few newspaper reports published on the subject; and (3) most importantly, a content analysis of the La Nuestra Familia constitution which was 'leaked' through anonymous channels to the author. The organization was founded by rural Mexican inmates as a protection against the 'Mexican Mafia' consisting of urban Mexican inmates. The group has successfully expanded its influence into the street and is now involved in the standard activities of organized crime. At the very center of the organization is the Supreme Commander (El Neustro General) surrounded by a central core of officers and hard-core soldiers. At a second level of involvement are the 'loose members' who may not be total participants in the activities. The peripheral members ('fencewalkers' or 'snakes') are not considered true members. As with other criminal organizations, a strict code of honor is articulated and enforced on pain of death. Primary loyalty is vested in the Familia rather than individual needs. Although this single case cannot be generalized, several inferences can be drawn: (1) organized crime is split up in various racial and ethnic groups which do not necessarily cooperate and may even be antagonistic to each other, and (2) organized crime groups fulfill the needs of their members--in this case, physical protection in prison or, in other cases, economic or political protection in the urban ghetto. The article includes organizational diagrams, some footnotes, and 27 references.