Patients’ adherence to their doctors’ instructions is important for successful healthcare outcomes. Moreover, previous studies have shown that doctor-patient communication greatly affects patient adherence (Davis, 1968a; Francis, Korsch, & Morris, 1969; Fremon, Negrete, Davis, & Korsch, 1971; Gunby, 1982; Hall, Roter, & Katz, 1988; Hall, Roter, & Rand, 1981). Physician communication skills, however, are a difficult variable to define and study. This thesis describes the linguistic construct of the Doctor, Educator, and Fellow Human voices detailed by Marisa Cordella (2004) in her discourse analysis of medical interviews. These voices are used to describe the goals of a doctor-patient interaction and the strategies used to accomplish them. Analysis of existing studies involving patient-physician communication demonstrated that any use of the Educator or Fellow Human voice increased patient adherence, whereas the benefits of using the Doctor voice could be negated by the absence of another voice. The thesis offers a physician voice-based discourse analysis method that was used in examining transcripts of patient-physician interaction. The results showed that Cordella’s physician voices were associated with patient adherence and therefore may be useful for examining medical communication in future studies. Finally, recommendations are offered regarding physician education when communicating with patients.