本研究旨在以質的研究法描述、分析、與詮釋國中理化教師教學改進之決策行為，研究對象為兩位具有多年教學經驗五天參與暑期進修之在職國中理化教師。經由對兩位教師在暑期進修及學期中的教學前後約半年的非參與性觀察，以及開放性問卷、晤談、文件的收集、教學錄影、錄音等途徑所得資料，八三角校正和恆常比較法來建構、分析，以獲知研究結果。
研究結果顯示：壹、個案教師對教學改進之認知較偏向於實務取向，其特色是融合著多年的學習、教學與進修的經驗，建構了一套有關教學與學習本質的認知基礎，引導其對教學改進的所思所行。貳、個案教師的教學改進雖係配合在職進修並透過行動研究的方式融合著計畫、行動與反思的循環歷程，但其決策行為仍具有強烈的自主性，往往以其個人的主觀判斷引導思維與情境、事件約互動。參、影響個案決策行為的因素有個案對教學改進的認知、人格特質、與時間等外在因素，這些因素對兩位個案的影響截然不同，甲老師的決策行為與其認知較為一致；乙老師則較注重現實客觀情境因素的限制，並未完全將其認知落實在教學決策行為上。
本研究最後提出對科學教育、師資培育、資深科學教師、科學教學、研究方法等五個向度之啟示。並對教師改變，不同個案、學科、學校的差異性比較，行動研究，及學生的學習反應等方面的後續研究提出建議。

The purpose of this study was to describe, analyze, and interpret second, cience teachers'' decision making in improving their teaching practices Qualitative research method was adopted to explore the teaching practices of t experienced secondary science teachers who were participating in the summer professional development program. Data were obtained from a half year classroom observations of the teachers when they were involved in teaching and in attending the summer school, and from questionnaires, interviews, related documents, and videotaping of their classroom teaching. Research findings were constructed by analyzing the data using triangulation and the constant comparative method.
The results of this study included three key findings. Firstly, the cognition of both experienced secondary science teachers were very practically oriented with regard to improving their teaching practices. Their thinking and teaching behavic were guided by a knowledge base about the nature of teaching and learning which they constructed from synthesizing the experiences gained from their learning, teaching, and participation in the summer professional developme program. Secondly, although the efforts in their improvement of teaching were part of the professional development requirement in doing action research works whiiembraced the planning, action and reflection cycle of the teaching practices, both teachers displayed strong initiatives in their decision making behaviors. Their ways of thinking and reactions to the instructional contexts and events were often guided by their subjective judgments. Thirdly, factors which affected the teacher decision making included, among other things, their cognit-ion of improving teaching practices, personal traits, and time available for teaching. However, the extent as to how these factors affected both teachers'' decision making varied greatly. One teacher was more consistent in his decision making and his cognition of improving teaching practices, while the other was more concerned about the constraints of the external reality and showed less consistency in this regard.
The implications of this study were discussed in terms of science education, teacher''s education, experienced science teacher, science teaching , and research method. Suggestions were also made for future researches in the areas of teacher changes, the comparison of different cases, subject matters or school environments, action research, and the resulst of students''s learning.