Although medical discourse has been explored from both qualitative and quantitative perspectives since the 1980s, there have been few corpus-based linguistic analyses of doctor-patient and nurse-patient interactions. Such analyses are useful both to identify the linguistic features characteristic of medical interaction and their functions within the health care context, and also to provide insight into language needed for teaching and training medical providers. This chapter will explore the use of linguistic features associated with medical discourse in two contexts: nurse-patient interaction and doctor-patient interaction. In order to identify distinctive features of spoken medical discourse, the nurse-patient and doctor-patient interactions will be compared to casual face-to-face conversation. Lexico-grammatical features that have been identified as important to effective medical encounters, such as stance devices (e.g., modals), narrative structures (e.g., past tense), personal pronouns, and questions will be investigated across three corpora. The functions of the linguistic features will be interpreted in relation to the situational characteristics of each register, including the speaker's role in the interaction. The results show similar patterns across the two medical contexts in comparison with conversation. This lends support to previous research that has compared nurse-patient interactions with conversation (Staples and Biber, Corpus analysis for descriptive and pedagogical purposes: ESP perspectives, 2014). However, there are also important distinctions between the two medical contexts, which are related to the speaker role (doctor vs. nurse) and the setting of the interaction (primary care clinic vs. hospital). The findings have implications for the sociolinguistic study of health care communication as well as the teaching and training of both native speaking and non-native speaking English medical providers. In particular, many of the linguistic features are associated with patient-centered care and the building of patient rapport.