ABSTRACT Although most scholars agree that "topic" may be defined as "what a message is about", topic is still one of the least understood concepts in linguistics. The general objective of this study is to integrate different types and levels of topic: entity, proposition, text, speaker, and interactive topics. The method will be to analyze how variation in language use is related to topic. The focus will be on variation in clause order (between main and subordinate clauses), and variation in referring terms, and how such linguistic variants are situated in discourse and interaction. Because topic realization depends on communicative processes that are social and expressive, as well as referential, there will also be an analysis of how topic- related variation in clause order, and in referring terms, is related to speakers' social identity (social class and gender). The study differs from past analyses of topic in several ways: 1) the study aims to integrate five different types and levels of topic; 2) the study includes an analysis of the information status, as well as the topic status, of entities and propositions; 3) the data are diversified in terms of discourse mode; 4) the discourse in which topics are encoded is itself analyzed; 5) the study examines social differences in the encoding of topic. The project is relevant to the study of topic, information status, linguistic variation, syntax and discourse, and social differences in language use. It also has implications for variation theory and analysis, and our understanding of discourse coherence. Finally, it will provide connections between interactional and correlational sociolinguistics, and help align the concerns of formal and functional linguistics.