Personal interaction between health policy makers and researchers is widely seen as the key to enhancing research use, but there are also increasing demands that policies be based on syntheses of the available evidence. A potential paradox arises in that whilst interaction may result in greater use of the evidence it might also lead to a partial selection of evidence, not consistent with a systematic overview. The "interfaces and receptor" model, developed for a World Health Organization project analysing health research utilisation, facilitates examination of these issues. It highlights the importance of analysing the different cultures of researchers and policy makers, and the permeability of the various interfaces between them. It also focuses attention on the key role that policy makers play as the receptors, or receivers, of research and how issues of training and organisational culture and structures might be of increasing importance in assisting research to move up the various steps of the ladder of utilisation. Case studies taken from previous work how the interfaces and receptor model can be applied to: help analyse research utilisation; explore the paradox; and contribute to an evidence-base for policies aimed at building effective research systems.