In earlier studies concerning how do schools as organisations facilitate teachers´ professional development and well-being connection between teachers' work-related well-being (both in perceived psychic and physical well- being) and developmental activity, especially at community level, have been shown (Meriläinen & Pietarinen 2004). The aim of this study was to examine closer factors behind teachers' work-related well-being and the meaning of stress for developmental activity and accordingly for professional development. Recently the research interest to understand the relation between the working environment and individual teacher's professional development from to viewpoint of teachers' well-being has increased (Kyriacou 2001). The grounds for this argument can be raised from both theoretical and practical demands. Theoretically various definitions related to the concept of teachers´ professional development include implicitly the assumption that teachers' perceptions about their professional development illustrate also their perceptions about individual work related well-being in a teacher community (Wilhelm et al.2000). In the theoretical framework of this study the teachers´ work related social, mental and physical well-being is defined and conceptualised from the viewpoints of 1) changes in nature of teachers' work, 2) teachers´ professional self-efficacy and -respect, 3) teachers' professional development and the 4) characteristics of the school organisation. The empirical part of this study conducted by a large survey in which about 700 primary and secondary teachers from the eastern part of Finland had an opportunity to answer the questionnaire within one day when they participated (November 2003) in regional in-service training event. The questionnaire includes modules that contain several items (attitude scales) and open-ended questions that are planned on the basis of conceptualisation of teachers' work related well-being. When examining closer the causes and consequences behind the teachers' perceived stress it was found out that teachers' willingness to develop their work and conceptions of in-set system differed in accordance with perceived stress. It seemed that more teachers were stressed less they were willingness to develop and more they were unsatisfied to the present in-set system. The results can be exploited at least in two different levels. Firstly the data will make it possible to understand better the meaning of teachers' work-related well-being from the point of view of professional activity and development. Secondly the conclusions of this study will be used when we try to find out how to improve teachers' work-related well- being. The factors behind teachers' perceived stress will be discussed especially from the point of view of the pedagogical leadership.Keywords: teacher's work related well-being, stress in teachers' work, professional developmental activity and professional development, school organisation, pedagogical leadership.