Immigrants from one dialect region to another acquire features of the new dialect with varying degrees of proficiency. In modern societies regional mobility is commonplace, and for modern dialectology, involved as it is with variability, mechanisms of change, and adaptation, it is a rich source of hypotheses. This article postulates eight general principles by which immigrants adapt dialectologically to their new surroundings, based mainly on results of a developmental study of six Canadian youngsters in two families who moved to southern England in 1983 and 1984, with supporting evidence from several other studies. The principles provide a set of empirically testable hypotheses about the determinants of dialect acquisition.