This paper describes a university research program, the Teacher Model Group, which developed a theory of teaching in context, examining how and why teachers make specific decisions and take specific actions as they teach. The teacher model includes descriptions of teacher beliefs, goals, and knowledge. Two core assumptions underlying the model are that the activation levels of beliefs, goals, and knowledge at any moment will be assigned so that the highest priority beliefs, goals, and knowledge are consistent and mutually supportive and teacher actions are selected in a way consistent with the teacher's current highly activated beliefs, goals, and knowledge. The paper describes models and the modeling process, characterizes the general structure of the theory of teaching in context, and examines the means by which specific models of individual teachers engaged in the act of teaching are constructed. It describes representational forms that the Teacher Model Group uses for descriptions of teaching and presents four case studies involving a relatively new educator who taught traditionally, an experienced teacher who taught non-traditionally, and two very experienced teachers who modeled one lesson with ease and had trouble modeling another. The paper discusses prospects, strengths, and limitations of the model. (Contains 68 references.) (SM)