With over 375 participating communities worldwide, well-established networks in many parts of Europe, North America and Australia, and with initiatives in many developing countries, the Healthy Cities movement is widespread and, in many jurisdictions, continuing to expand. As the movement matures, interest in the evaluation of its successes and potential limitations has grown. But as yet there has been little systematic assessment of evaluation strategies for Healthy Communities (HC). In this paper, a number of principles are advanced as being fundamental underpinnings for knowledge development and evaluation in, of and for HC initiatives. It is argued that a participatory action research approach is called for, but also one that includes a critical social science perspective on health, as part of attempts at the local level to define appropriate conceptual models of HC practice from which to ground knowledge development and evaluation efforts. It is argued that one should pay close attention to the theoretical, ethical and political issues that attend the evaluation of HC initiatives, since 'evaluation' has become a politically and ideologically charged issue. In a subsequent paper (Part II, to be published in Vol II, No. 4), a number of substantive foci are reviewed as potential bases for evaluation within the parameters of the principles and methodology described in Part I.
