The linguistic situation in the Grassfields of Cameroon poses a problem, indeed a challenge. Basic vocabulary counts and shared lexical innovations point to one language classification and historical interpretation; but innovations in noun-classes do not agree and point to another (Voorhoeve 1976). To reconcile these findings in a consistent historical explanation, one must have recourse to some hypothesis as to the past relationships among the speakers of the languages. Such a hypothesis must be controlled by whatever can be known about the sociolinguistic history, as it were, of the area. In recent ethnohistorical research, I have been able to reconstruct a nineteenth-century pattern of multilingualism as an essential part of the social and political fabric of the Grassfields. Of the three hypotheses that might be advanced to explain the present language situation, the third is best supported by this reconstruction and other evidence. Further work is underway to test the hypothesis. In the meanwhile, the case shows the necessity of sociolinguistic as well as narrowly linguistic reconstruction in explanation of actual cases of change.