This paper discusses the need for the renewal of teacher education programs in Finland in order to bring practicing professionals into contact with new knowledge and ideas. To inject new knowledge requires a theoretical understanding of the mechanism of professional change and the process of evaluating professional development. The central factor governing the effect of professional development upon classroom teaching is the ability of teachers to be reflective about their practice, i.e., to reflect upon the origin, meaning, and consequences of their actions. The operative concepts in group process are personal pedagogical knowledge (content knowledge), broken down into metacognitive knowledge, construction, and conceptual knowledge; professional development (gradual changes in behaviors and perceptions of student teachers); and self-evaluation (qualitative judgments about one's thoughts and behavior). Self-study is a part of ongoing professional self-development which needs support, facilitating, encouragement, time, and teaching. (Contains 42 references.) (CK)