This article focuses on understanding teaching activities, especially in the field of health science, as a set of tasks and actions that teachers undertake when transforming scientific knowledge into curriculum contents and actions. There are several ways to address this issue. Some authors identify specific roles and qualities of teachers structured as variables and dimensions. Others use the term competencies, applied as skills, aptitudes or abilities to do something very well or duly intervene in a certain matter. The term competence, although not yet clearly defined, is used in this work because it is widely used in Health Sciences education. Some definitions are reviewed. Teacher's competencies in the following areas recognized: those related to specific professional skills, in contents organization, in learning skills, in new information and communication technologies, in evaluation and in social and ethical areas of educational practices.