Mathematics is considered to be one of the key areas for growth and development in Egyptian schools (Monk et al., 1999). Therefore, reforming mathematics education has been given priority by the Egyptian Ministry of Education. Accordingly, a particular emphasis has been given to the professional development of mathematics teachers. This paper is a case study of the role of the Egyptian National Network for Distance Training (NNDT) in development of mathematics teachers’ knowledge and in reforming teachers’ practice in schools. This paper concludes with some suggestions for the effective use of the network in teachers’ professional development