We describe adherence to a three group randomised controlled trial that involved aerobic exercise therapy (N=34) and exercise-placebo intervention (N=36) or usual care (N=38) in women treated for breast cancer. We also investigated relationships between routes of trial recruitment, socio-economic characteristics, health behaviours, cancer treatment regimen(s) and subsequent adherence to the interventions. Women who had completed breast cancer treatment 12-36 months previously were randomised to one of the groups. The intervention groups attended an exercise facility three times per week for eight weeks. A total of 77% of the aerobic exercise therapy and 88.9% of the exercise-placebo groups attended at least 70% of prescribed sessions. The percentage of women achieving 30min of aerobic exercise per session steadily increased during the intervention but many women were not able to achieve this goal. Routes of trial recruitment, socio-economic characteristics, health behaviours and cancer treatment regimen(s) were not related to intervention. Exercise therapy participants were able to comply with the progressive nature of the aerobic exercise intervention, although some women were not able to achieve 30min of aerobic exercise per session by intervention completion. Research is still required to tease out all the potential determinants of exercise in this population.