This is a theoretically informed study on code-switching presenting a completely new approach to code-switching between tonal and non-tonal languages, here Vietnamese and English. It is also the first large-scale study of Vietnamese-English bilinguals. The book deals specifically and comprehensively with the patterns of code-switching among the Vietnamese settling in Australia. Beginning with a general description of Vietnamese language and culture and the sociolinguistic consequences of Vietnamese people leaving their home country, the author moves on to discuss the universal principles constraining the distribution of intra- and inter-sentential code-switching with a particular focus on the social and linguistic aspects of Vietnamese, which include the Vietnamese system of personal reference and an analysis of Vietnamese tones. The book provides the reader with a solid theoretical linguistic background and an insight into traditional Vietnamese society through a comprehensive analysis of sociolinguistic and pragmatic aspects of switching pronouns to establish or change relations between speakers. Other aspects covered include social attitudes towards personal status, language contact, bilingualism, and the significance of tone relationships in Vietnamese which bear on the phonetic nature of the associations between syllables adjacent to English portions of utterances and the English words themselves.