Decision aids for health service users facing decisions about screening have been developed for controversial tests (such as that for prostate specific antigen as a screen for prostate cancer) and tests in which outcomes are value laden (as in some prenatal tests). The potential usefulness of decision aids in established screening programmes (such as those offering mammography to women over 50 in the United Kingdom) remains to be explored. In principle any decision about screening test acceptance may be sensitive to individual preferences and could be supported by an appropriate decision aid. Decision aids might also help reduce some of the problems currently associated with public misconceptions about screening. Objections to the promotion of individual choice regarding screening tests usually take the form of concern that this will lead to unacceptable losses in terms of population health gain and health system efficiency, or of fear that individuals will choose options that are wrong for them. The introduction of decision aids could alleviate both of these objections to some extent. Decision aids could encourage people to consider the social as well as the individual consequences of their choices and they should promote choices consistent with personal values. Although there are strong arguments in principle for introducing decision aids into established screening programmes, their potential needs to be confirmed in empirical evaluations and there may be many contentious decisions and practical challenges to be overcome in order to implement them.