The use of theories in Nursing reflects a movement in the profession towards the autonomy and delimitation of its actions. It is, therefore, extremely relevant that theories may be analyzed as for their applicability to practice. The object of this study is to make an analytical-descriptive study of Peplau's Theory of Interpersonal Relations in Nursing from the model of analysis proposed by Barbara Barnum. Among the structural components that may be analyzed in a theory was chosen the element "process", a method recommended for the development of nursing' actions, which was submitted to Barnum's criteria of usefulness. The assessment showed that Peplau's theoretical presuppositions are operational and may serve as a basis in any situation in which nurses communicate and interact with his/her patients.