A framework of laboratory, clinical and consumer evaluations is being developed that will allow a scientific assessment of whether use of new technologies and tobacco products is likely to result in (1) substantial reductions in exposure to tobacco smoke toxicants and (2) how such reduced exposure might relate to a reduction in risk of smoking related diseases. This PREP Assessment Framework outlines the different stages of evaluation including product stewardship of new technologies, smoke chemistries, consumer behaviour and sensory testing as an initial stage before clinical studies. These latter studies estimate any reduction in exposure to smoke toxicants and possible changes in biomarkers of effect. The significance of any biological effect from clinical studies is supplemented with a series of concurrent in vitro biological assays of disease processes. The assessment and proposed dossier will be in a format similar to the CTD used in pharmaceutical submissions, based on a "weight of evidence" approach. In the longer term these assessments will also include computational toxicological modelling as a means of integrating the data from the different studies. Although the results from controlled laboratory assessments and clinical studies should give some indication of individual's reduced exposure and changes in potential risk, it is anticipated that the wider population effects of these prototype products will have to be assessed in larger scale studies, such as limited "blind" test markets with market surveillance.