the purpose of this study was to use the constructs of the theory of planned behaviour to gain a better understanding of older adults participation in strength training. two hundred participants aged 55 years and older completed a questionnaire which assessed the constructs of the theory. participants were classified into four groups based on self reported levels of participation in physical activity. the groups included strength plus aerobic trainers (sat), strength trainers (st), aerobic trainers (at), and non-trainers (nt). results revealed no significant differences between the groups on attitudes. both the ats and the nts differed significantly from the two strength training groups on perceived behavioural control. the nt group also differed from the two strength training groups on subjective norms. the ats were significantly different from the sats on behavioural beliefs and both the ats and nts were statistically different from the sats on control beliefs. subjective norms and perceived behavioural control were the strongest predictors of intention. these findings provide information about the constructs that should be targeted in intervention programs designed to increase strength training participation in the older population.