Action research is defined as using research activities to develop concrete societal practices. Action research understands the change of practice as being already a central aim of the research process itself, and it also seeks to contribute to the professional development of all participants in the particular field of study. Even though (or maybe even because) action research has a long history in the literature, there is a wide variety of interpretations of it. These range all the way from research supportive, via interactive, to emancipatory approaches. There is also a broad range of objectives covering both improving professional environments and generating results of general interest. This paper explores the spectrum of justifications given for action research with a specific focus on science education. Two completely different examples of action research selected from Israel and Germany help illustrate the diversity of the topic. The Israeli case focuses primarily on the professional development of a group of teachers; the German example hones in on the development of suitable curricula and lesson plans for wide dissemination. Comparison of these two projects is embedded in a theoretical framework which categorizes the different action research modes and contemplates teachers' professional development. The aim of this paper is to reflect upon the common potential inherent in differing forms of action research on science education, including the aspect of professional development among teachers.