Women aged 50 and older are disproportionately affected by breast cancer, not only in terms of new diagnoses, but also in terms of survivorship. Approximately 85% of women who receive a first diagnosis of breast cancer are aged 50 and over, thus older women constitute the largest group of breast cancer survivors. Yet, few studies have focused on evaluating whether physical activity and exercise interventions affect long-term symptoms, physical fitness and function, and body composition of older breast cancer survivors. Due to the combined effects of breast cancer, related treatments and aging it is likely that exercise is even more beneficial for older breast cancer survivors than for younger survivors. Along with the cancer-related symptom of fatigue common to cancer survivors, older survivors face age-related declines in bone and muscle mass, muscle strength, bone health and physical function (gait and balance) that are likely exacerbated by reduced physical activity in survivorship and side effects of adjuvant cancer treatment. All women, regardless of age, are at risk for breast cancer recurrence. Recent epidemiologic evidence suggests a link between exercise and reduced risk of cancer recurrence in breast cancer survivors. Strength training is specifically suited to reverse or slow age-related declines in bone, muscle, strength and function and has shown promise to reduce cancer-related fatigue. However, no controlled trials of strength training in older breast cancer survivors have been conducted.