Self-efficacy is an important mediator of behaviour change. We have developed a brief measure of self-efficacy related to ability to make dietary changes to lower serum cholesterol. An initial pool of 37 items was tested on 85 third-year nursing students. Factor analysis revealed two primary factors ('self-efficacy for resistance to temptation' and 'self-efficacy for change') composed of 13 items. This instrument was validated in a sample of 125 blue collar workers. Analyses confirmed that the scale structure accounted for 37% of the variance. Evidence of discriminant validity was provided by moderate correlations between factors (r = 0.41). Item-scale correlations also supported the discriminant validity. Cronbach's alpha ranged between 0.7 and 0.79 for both factors. This short instrument might be useful as an adjunct tool to identify potential responders for cholesterol modification interventions, to help understand the determinants of dietary behaviour changes and to guide the tailoring of interventions toward specific client/population subgroup needs.