Exercise has important health benefits, but a large proportion of the population is physically inactive. We examined the prevalence of stages of readiness to exercise and their relationship to self-efficacy and to the costs and benefits of exercising in samples of 1093 employees in and around Providence, Rhode Island, and 801 employees in Adelaide, Australia. In both samples, 40.6% of respondents had not yet begun to take action (not thinking about starting to exercise or thinking about it but not doing it), while 59.4% were at some phase of action (exercising some, starting to exercise regularly, exercising regularly). Scores on self-efficacy items and cost-and-benefit items significantly differentiated employees at extreme stages. In contrast with those who exercised regularly, employees who had not yet begun to exercise had little confidence in their ability to exercise and saw exercising as having nearly as many costs as it had benefits. There is the potential to enhance the impact of exercise interventions by targeting them so as to address factors related to these different stages of readiness to exercise.