The aim of the present research was to determine if implicit dispositional motives, which operate largely outside of conscious awareness, can provide any incremental prediction of health-related behaviour and reactions to health-promotion messages over that obtainable through measuring only explicit dispositional motives. To this end, an initial objective was to develop a measure of implicit dispositional motives that would avoid some of the drawbacks (low internal reliability, high time investment) of the traditional implicit motive measure. In a series of studies, the present research tested the validity of a measure of implicit dispositional motives, developed a set of psychometrically coherent stimuli to represent implicit motives, developed a framework of the effects of motives on sun-related behaviour and risky sexual behaviour, used this framework to establish the incremental prediction that implicit and explicit dispositional motives provide for these behaviours, and examined the influence of implicit and explicit motives on reactions to health promotion messages. Results suggest that implicit dispositional motives do provide incremental prediction of sun-related behaviour over that provided by measuring only explicit dispositional motives. Effects of explicit dispositional motives on behaviour are mediated by participatory motives. Effects of implicit dispositional motives on behaviour were also mediated by ( explicit) participatory motives. Explicit dispositional power motive is a primary predictor of both sun exposure behaviour and risky sexual behaviour. In1plicit dispositional achievement motive protects against sun exposure behaviour. Results also suggest that both explicit (participatory) motives and implicit (dispositional) motives influence reactions to health promotion messages. It is concluded that health promotion messages should be tailored to take into account both the explicit and implicit motives known to underpin a health-related behaviour.