This paper will report on the mediation effects of the key artifacts upon teacher participation in two school-based leadership development projects in schools in 2005 and 2006 respectively. This structural approach to taking up more curriculum responsibilities by the schools in Hong Kong was recommended by the Government in 2001, and yet there is little empirical evidence about its implementation and effectiveness. The projects will collaborate with two active schools, setting up two curriculum development teams in each to bring about planned innovations in pedagogy. The teams will conduct a cycle of curriculum activities in the first and second semesters, reviewing the current curriculum, planning an innovation, and designing and implementing it in classroom settings. Afterwards, each team will conduct reflection for further improvement. All participating teachers will be interviewed 4 times during participation. All meetings and tryout lessons will be video-taped. The interview data will be analyzed by identifying and classifying key emerging themes which will illuminate our understanding of the participating teachers' experiences in the curriculum process. The meeting data will be analyzed using activity theory to identify the key factors that facilitate or constrain the effectiveness of the teacher participation. The findings will deepen our understanding of the effectiveness of teacher participation in school-based curriculum development.