This study of contact between the French and English language groups in Canada is based on an ecological approach, emphasizing factors such as population composition, residential patterns, occupational pressures and age and sex differences rather than cultural or psychological ones. Part 1 begins with a general discussion of the problems of language and ethnic relations in Canada and then presents a discussion of the demographic and institutional pressures which affect the linguistic situation. Part 2 deals with questions of bilingualism and mother-tongue maintenance. A wide variety of factors operative throughout Canada (sex, residential patterns, peer group contact, urban-rural factors) are examined; the role of occupation and industrialism in one specific city, Montreal, are then discussed in some detail. The relationship between bilingualism and language maintenance are then dealt with, the author devoting some time to developing a model to account for French mother-tongue retention that incorporates several factors considered. Finally, in discussing the implications of the study for research in linguistic pluralism and ethnic relations, the author concludes that the factors accounting for mother-tongue shift are different from those accounting for bilingualism and that mother-tongue maintenance plays an important role in differentiating ethnic groups in contact. (FWB)