School leadership is the most important factor in the improvement of schools. Now it is widely accepted that headteachers need both pedagogical and managerial skills to lead a school. This can be achieved through leadership training programs. In many countries including Pakistan, teachers are mostly promoted to headship positions without their having management and leadership skills in schools. Therefore, the training becomes important for those headteachers who have been promoted to headship positions on the basis of their seniority or teaching experience. The School Leadership Training Program (SLTP) was an in-house training program, which was carried out for the headteachers of AKES, P schools in the Northern Areas. This study is about the impact of SLTP on the knowledge and practices of the Headteachers (HTs) who attended the training program. This inquiry presents the impact of the training program in terms of the sense of self-efficacy, knowledge acquisition, practices and performance of the HTs. The study was carried out in January- February 2004 in four schools of the Aga Khan Education Services, Pakistan, two Field Education Offices, and the Training Program Office of the AKES,P Northern Areas, Gilgit. Qualitative and quantitative research methods were used. Data was collected through interviews of the HTs, teachers, and education officers and a program coordinator, and through document study of schools, FEOs and SLTP related to the practices of HTs, and their staffs. For data analysis the grounded theory of data analysis was used. This study reveals that SLTP had made an impact on the perception, knowledge, practices and performance of the headteachers. The impact of the training program was ascertained on the beliefs, attitudes, and practices of the HTs as well. The research also exposed factors that facilitated or hindered the implementation of the knowledge and skills learnt by the HTs during the training. The major facilitating and hindering factors remained the innate qualities of individuals, system support, suitable working conditions, academic knowledge, and needs based training.