The main aim of this thesis centred on what made effective professional development programs. As a particular case study data was collected on those programs sponsored by the Melbourne Catholic Education Office. Teachers from three schools in the North Western Metropolitan Zone of Melbourne, Australia, the principals from the three participating schools and training staff from the Catholic Education Office in Melbourne became the subjects of the study. The data collected from questionnaires was analysed in order to ascertain whether there were any common trends as to what the teachers thought was needed in effective professional development programs. The interviews with the participating principals and training staff were taped and later analysed in order to determine what they believed was the purpose of professional development and whether the programs currently being offered were effective. In addition, a list of characteristics of effective professional development was developed from the relevant research literature. The analysis of the above data was used to develop a model of effective professional development. The design of this model is cyclical. A main characteristic of the model promotes the reflection by both the participants and the training providers on what has occurred during the program and this process of reflection contributes in later development of programs in similar areas. It was also concluded that the needs and expectations from professional development of teachers and principals were different to what has been expected in past research projects. Both the teachers and principals expected that they would not be solely immersed in theory or in activities that may be used in the classroom. Instead they hoped to gain a knowledge of activities that are based on theory and develop an understanding of how these activities may be used and how they will assist in student learning. Hence, the link between the theory and its application was believed by teachers and principals to be of primary importance in professional development in order to maintain high teaching practices and in turn result in improved student learning.