In this paper, the concept of "invisible ethnic" is used to refer to an individual who is identified as different by dominant members of society and who is caught between an ancestral identity and culture on the one hand, and a wish to be assimilated, on the other. This concept is discussed in relation to Stonequist's "marginal man" and the social processes engendered by the phenomenon are examined. The position of immigrant and native ethnic groups in the United States and the pressures on them to conform to the dominant culture are contrasted with true opportunities for and costs of assimilation. Three modes of adaptation that Stonequist discusses as possible avenues out of the marginal self conception (the assimilationist role, the intermediary role, and the nationalist role) are considered. The concept of the marginal group is proposed for identifying the group manifestation of the psychological sense of inferiority and alienation described by Stonequist. This concept is then discussed in terms of its implications for ethnic group dynamics in a rapidly changing society such as the U.S. The rise of civil rights and ethnic organizations is cited as a consequence of the marginal group phenomenon. Also recognized is that this type of assertion of ethnic identity has strong implications for continuing conflict in intergroup relations. (Author/GC)