This paper will explore what motivates teachers to participate in development projects, involving experimental teaching, and especially what the nature of pressure for change means for the engagement of the teachers. Thus, it is not dealing with TPD organized as ordinary courses, but digs into the potential of more long lasting development projects – and how different organizations of the projects can lead to different engagement. The analysis is based on research the author performed on two large TPD initiatives for the upper secondary education (the gymnasium) in Denmark. The first took place in the 90ies as a quite open, self-directed and decentralized initiative. The other was a more central organized initiative taking place in the 00es. They are finally put into perspective with recent experiences with TPD activities in the 10s. One of the intentions of the paper is to show the importance of the societal and organizational framing of a professional development project, therefore the contexts for the different projects are described quite thoroughly.