This article takes a critical approach to the study of the SARS notices and their translations from the perspective of discourse analysis. Drawing upon the insights of systemic functional linguistics (SFL) and critical discourse analysis (CDA), this study explores how language is used by different governmental institutions in shaping their social power and hierarchy. By conducting a comparative study of the SARS notices and their translations, focusing on speech roles, speech functions, modality types and modality orientation, the authors argue that choices made in producing the texts reflect the institutions' social roles and their relationship with each other and with the audience. They also argue that the application of concepts from SFL in detailed text analysis and from CDA in the overall discussion may better reveal how different models of discourse analysis can supplement each other and be applied to translation studies.