This thesis reports and analyses the perceptions of curriculum change of Israeli secondary headteachers who led and managed the implementation of the pilot of a significant change to the curriculum known as "Bagrat 2000". "Bagrat 2000" represents an approach to reforming and reorganizing secondary education studies.;The research paradigm is interpretive. The data were collected mainly from semi-structured in-depth interviews with 19 headteachers. The 19 schools that these headteachers manage are from the different educational sectors and different regions of the country.;The analysis offered was based on a typology of the headteachers' perceptions according to their preliminary decision-making process in entering "Bagrat 2000". Three types of headteachers were found. Type 1 - those who had decided alone to participate in the curriculum change, Type 2 - those who had applied a participatory decision-making process and Type 3 - those who had begun, in their schools, the changes in teaching, learning and evaluation methods prior to "Bagrat 2000".;The presentation of the findings shows that no significant differences were found in the personal data of the headteachers or the schools' characteristics. All the headteachers perceived the change as a requirement. No significant differences were found in the different stages of the implementation, as "Bagrat 2000" is a combination of imposed and voluntarily change. In addition, although the issue of partners in the staff was perceived as a very important goal, there was a gap between this perception and the actions taken by Type 1 headteachers. Differences were found between the types when focusing on opposition. However, all the headteachers, regardless of the type they belonged to, could be described as 'transformational' and 'people-oriented' leaders. Yet, when the change was not by mutual agreement between partners in the enterprise, the leadership included both 'transactional' and 'task-oriented' characteristics.;One of the central issues that any headteacher will have to deal with is the constantly evolving nature of the curriculum. It is believed that the research outlined in this submission will be relevant to our developing knowledge of headteachers' perceptions of curriculum change.