Ph.D. / The purpose of this study was to investigate the ways in which Social Network Analysis can be used to enhance the conitinuous professional development of the Mathematics teachers of a secondary school. With this in mind a literature study was first undertaken in order to clarify exactly what is meant by a Social Network Analysis perspective, online social networks and the continuous professional development of teachers. The study was framed in a Multi Method Mixed Methods framework to enable the integration of a Design Based (DBR) study and Social Network Analysis (SNA) in different phases of the overarching research. The purpose of the DBR study was to design and develop an online social network to provide the Mathematics teachers of sufficient opportunities for continuous professional development. The assumtion was made that the online social network will develop into a Learn 2.0 technology if a) it could provide access to appropriate content, b) teachers could use it to develop own professional development opportunities, c) it could provide opportunities for collaboration between the teachers and d) if it could provide opportunities to connect with those teachers who could contribute their Professional Development. This study refers to the ties which were used to enable the flow of information, knowledge, advice, leadership, support, experience and concrete artefacts (documents) as a teachers’ Personal Development Network. From a SNA perspective the personal development networks of the teachers cannot be fully understood without studying the social network in which these ties are embedded. I refer to this network as the Development Network. The development network is at any given point a stable social construct, but it changes as soon as new ties vii are formed or old ties disintegrate. Therefore a Social Network Analysis was done before, during and after the intervention to explore the development network to understand, explain and predict the effectiveness of CPTD. The findings show that DPO.com (the online social network) provided the teachers of sufficient CPTD opportunities and developed during the course of the study into a Learn 2.0 technology. It also shows that SNA provides an effective method to understand and predict the CPTD of the Mathematics teachers.