Teachers increasingly find themselves facing new demands and changes, which they have to realize in rather unfavorable working conditions, e.g. a lack of time and resources. As a result, they experience increased work pressure or "intensification" (Apple, 1986; Ballet, Kelchtermans & Loughran, 2006). The principal, however, appears to play a crucial role in the way teachers experience these working conditions and their possible intensification. Drawing on the data from a larger research project on primary school teachers' experiences of intensification, this paper disentangles the particular mediating role of the principal in a teacher's experience of intensification. The conceptual framework for the study was based on literature on school development (Hopkins, 2000), micropolitics in education (Ball, 1994; Kelchtermans & Ballet, 2002) and "frame analysis" (Coburn, 2006). Since both the particular school context and processes of sense-making are central in the experience of intensification, we used a qualitative-intepretative approach and developed case-studies of Flemish primary schools (Merriam, 1998; Yin, 1994). Data-collection included several complementary research methods like semi-structured interviews of staff members, observations on-site and document analysis. Interpretative data analysis was done, first at the level of individual respondents and secondly at the level of the school. The results show that the way in which a principal mediates the impact of changes for teachers is not unequivocal and sometimes even paradoxical. The principal can "buffer" changes, but can as well strengthen and facilitate their (negative) impact (Ballet & Kelchtermans, in press). Since teachers expect the principal to "buffer" calls for changes, his lacking to do so has a clear intensifying impact. This way the principal actually becomes a facilitator of the calls for change and strongly contributes to the sense of obligation teachers experience in the calls for change. Rather than facilitating the calls for change, principals have to find a proper balance between the compelling character of changes and the specific characteristics of the school team (capacities, sense of workload). However, this does not mean that if teachers get "time and space" to deal with the changes in their own way, this pressure automatically disappears. Principals often show paradoxical leadership. On the one hand they give teachers the time to become familiar with the changes and to decide on the pace of their implementation, while on the other repeatedly sending out the message that all changes have to be effectively implemented as soon as possible. The intensifying impact of this double message can be reduced if principals use an implementation plan, in which not only the changes are dealt with in a systematic way, but also in a way that links the changes with the school's "mission" (core goals).In this paper we present and illustrate several patterns in the actual mediating impact by the principal. All patterns show that acknowledgement of teachers' own task perception and allowing them to participate in decision-making on the implementation are crucial conditions to minimize the negative intensifying impact. Ballet, K., & Kelchtermans, G. (in press, 2007). Workload and willingness to change. Disentangling the experience of intensified working conditions. Journal of Curriculum Studies.Ballet, K., Kelchtermans, G. & Loughran, J. (2006). Beyond intensification towards a scholarship of practice: Analysing changes in teachers' work lives. Teachers and Teaching: Theory & Practice, 12(2), 209-229. Coburn (2006). Framing the problem of reading instruction: Using frame analysis to uncover the microprocesses of policy implementation. American Educational Research Journal, 43(3), 343-379. Hopkins, D. (2001). School improvement for real. London: Routledge/Falmer. Kelchtermans, G. & Ballet, K. (2002). The micropolitics of teacher induction. A narrative-biographical study on teacher socialisation. Teaching and Teacher Education, 18(1), 105-120.