A study investigated four issues in language usage in the Republic of Congo: (1) the extent of intergenerational language shift; (2) patterns in language repertoire; (3) patterns of language usage among four generations, four topics of conversation, and four different locations; and (4) language usage differences in age groups. The languages considered are French (the official language), two national languages (Lingala and Munukutuba), and mother tongues. Data are drawn from interviews with 253 individuals of different ages and genders and in different locations (Brazzaville, towns, and villages). Results indicate that differences in parental and child language use are least in villages, greatest in the city, with subjects changing more often from mother tongue to Lingala or Munukutuba than to French. Mother tongue knowledge was virtually universal, with knowledge of national languages somewhat less common and French knowledge least common. Younger subjects were more likely to know French or national languages. Distinctive patterns of language use in different domains and by different age groups were also revealed. It is concluded that: national and official languages are gaining in importance; men know and use more French than women; each language type is relatively more important in some domains than in others; and Congo is in linguistic transition. (MSE)