The Mexican American bilateral extended family system was a part of the cultural heritage from Mexico or Spain and a family system developed as a social and cultural response to the cultural isolation and frontier environment of the Borderlands. As a social system, it mobilized members to work the land, protect family members and property against Indian raids, provide settlers for new settlements, carry out religious ceremonies and rituals, socialize the children, care for the aged, the sick, and the orphans, settle disputes, and provide leadership for the social group. Under the impact of either urban or rural poverty, the system collapsed, or at least suffered serious modifications. Where it did survive, it gave its members enhanced survival capabilities and strengthened their competitive situation. It also facilitated urbanization and industrialization. Among the middle and landowning classes, it facilitated the transfer of capital and personnel from agriculture into business and professional investments. It provided a base of political strength that enabled Mexican Americans to play political roles, except where the forces of discrimination were too strong or where Anglo American immigration swamped the Mexican Americans. Although the forces of urbanization and acculturation have weakened it severely, it still survives along with other family systems among the Mexican Americans. Indeed, it shows a hardy ability to survive, to adjust, and to persist. Even where it has almost vanished, its values still pervade Mexican American family systems. (Author/NQ)