This talk applies sociolinguistic theory to communities that were not originally the focus of variationist sociolinguistics. I first describe some well-known tenets of sociolinguistic theory pertaining to class, gender, peer influence, social networks, style and identity. These were initially developed in monolingual urban Western contexts for both practical and theoretical reasons. I apply them to English varieties that have developed in diaspora and postcolonial communities. Do the classic claims of sociolinguistic theory fall apart when we turn to situations of migration and bilingualism? Or do these cases help to refine theory? I suggest that mobile, multilingual, and culturally diverse populations do not undermine the idea of ‘orderly heterogeneity’ in speech communities. They do force us to recalibrate certain assumptions, but they also attest to the abiding power of deep sociological principles.