Hopkins, Bruce Joyce, Michael Huberman, Matthew Miles, and Virginia Richardson. But we have chosen to present our own experience and empirical data first and then, in Part 3, to show how this experience and data relates to models which have been proposed by others. We will address here methodological issues concerned with collecting and interpreting evidence of relationships amongst the many individual and situational factors associated with PD, and re-visit the arguments about 'process-product' research on PD. In the light of our experience, we will interrogate models of PD which have been proposed by others and attempt to move forward our total understanding of the process of the professional development of teachers for educational change. In conclusion, we will look at some current national practice in professional development, concentrating on the recent English experience of introducing 'strategies' into schools but referring also, by way of contrast, to the situation in the United States. WHAT'S THE PROBLEM? Why has the professional development of teachers already exercised so many good minds for so long? And how can we justify adding another book to this field? The answer to both questions must lie in the continuing demand from society in general (at least as interpreted by politicians and newspaper editors) for improvements in the quality of education.