This article is based on the findings of a study that examined the use of portfolios for assessment and learning purposes in an initial teacher education course in the Hong Kong Institute of Education. Progressive refocusing of the research led to an investigation of the extent to which the use of portfolios for such purposes promoted the development of reflective practice and teaching skills. Constraints and supports for the implementation of portfolios were identified through the use of observation, documentary analysis, surveys, video recordings and interviews with pre-service teachers and their lecturers. The implementation process and the teaching and learning outcomes are described. Teacher educators requested portfolio exemplars, more specific grading criteria and more examples to illustrate standards. Six principles that underpin the use of portfolios for assessment purposes, that emerged from an analysis of the research data and findings, are briefly described. An interactive CD ROM and a set of guidelines were produced as implementation resources. Details of these resources are provided. [Copyright of Assessment in Education: Principles, Policy & Practice is the property of Routledge. Full article may be available at the publisher's website: http://dx.doi.org/10.1080/09695940050118724]