Within the United States of America, French is of importance in only two areas, Louisiana and New England, the latter often being referred to as the Québec d'en bas for its high number of French-Canadian immigrants. Among the six states that constitute New England, Massachusetts is the one that attracted most of them, Québécois as well as Acadiens. Despite the high number of citizens of French-Canadian origin and the proximity to Canada, French has been losing ground as a langue du foyer in all of New England but especially in the southern part. This sociolinguistic study concentrates on the process of language decay among the French-Canadian population of Massachusetts. Based on a corpus consisting of 87qualitative interviews and a quantitative questionnaire survey of 392 questionnaires in 7 areas (covering the centers of French-Canadian immigration throughout Massachusetts),this study approaches the topic in a new, broader angle by encompassing the following aspects: ananalysis of U.S. Census data on ancestry and language use, an overview of the history of French-Canadian presence in Massachusetts, various specificities of the varieties of Canadian French spoken there, as well as ananalysis of the extralinguistic factors, such as the heterogeneity of the French-speaking population, and the intralinguistic consequences, such as unskilled code-switching,of language decay.