Longitudinal data (1871-1976) on the evolution of offical lang minorities in Quebec & English Canada are analyzed to assess factors in the declining use of langs other than Eng over the past decade. National statistics on ethnicity, first & home-use langs, & knowledge of official langs are detailed. The stability of the Francophone population from 1850 until the 1960s (approximately 30% of the population) is analyzed in terms of high French fertility & English immigration; loss of these demographic supports since 1960 & recent issues of lang mobility are discussed. The declining Francophone population outside Quebec & fewer English residents within that province are examined in terms of social conditions (eg, the influence of religion & of English economic control in Quebec); contrasts between institutional & territorial bilingualism models are underscored. 5 Tables, 1 Figure. Modified HA.