The aim of this study is to investigate the decision- making process of a teacher of English as a foreign language, more specifically the influent factors upon those decisions which are identified and analyzed in this research. The decision-making process is studied within a social cognitive view (WOODS, 1996), where the classroom is considered as being a multidimensional environment, with its social, affective and cognitive dimensions (ALLWRIGHT, 1988, 1996; VAN LIER, 1996). The influent factors are analyzed within an ethno-cognitive model developed by Woods (1996) and constituted of: (i) the events/action in the classroom, which together constitute a course; (ii) the planning that precedes these events and actions, where the teacher acts to create the course and elements that will form the events cited above; and, (iii) the understanding/interpretation that comes immediately afterwards, through which actions and events are understood and evaluated, feeding the planning process that in turn will influence future actions and events, starting a new cycle. Thus, this study is micro-ethnographic based (Erickson, 2001): its methodology focuses on people´s behavior in their work environment, describing its social culture and relations, searching to understand how these people see themselves and the group they are in. Thus, two classes of the same teacher were videorecorded. One week later the teacher was invited to tell the author what had happened as she watched the classes on the videotape. The researcher and the teacher decided to make use of the process called by many authors as storytelling (Calter, 1993; Casanave & Schecter, 1997; Clandinin & Connelly, 2000; Connelly & Clandinin, 1990, 1999; Trimmer, 1997; Witherell & Noddings, 1991; in Contreras E., 2000). The teacher´s decisions, in any level or moment of the course, are influenced by several factors simultaneously, and they also represent and signal her beliefs, assumptions and knowledge. Moreover, this study contributes to a better understanding of necessary content to be approached in teacher education courses that will help them in this constant decision- taking process.