Cancer and its treatment are associated with considerable distress, impaired quality of life(QOL), poor mental health, and reduced physical function. This is particularly true for womenwith breast cancer who receive multimodal treatment over an extended period of time. Manywomen undergo surgery and chemotherapy, which are often followed by radiotherapy. It isimportant to develop programs that can help ameliorate the treatment-related morbidity thataccumulates over time for women with breast cancer. Furthermore, given the stressful timedemands posed by radiotherapy treatment (patients typically receive treatment 5-days per weekfor 6 weeks) it is crucial that programs be easily incorporated into the treatment schedule.Research suggests that stress-reduction programs tailored to the cancer setting may helppatients cope with the acute effects of treatment and improve QOL after treatment. Yoga, anancient Indian science, incorporates stress-reduction techniques including regulated breathing,visual imagery, meditation, and various gentle stretching postures. Yoga may be particularlyuseful for women with breast cancer after surgery and while undergoing radiation treatmentbecause of the stress management and relaxation techniques and the gentle stretching thatshould facilitate recovery. Preliminary studies found yoga is useful for women with breast cancerundergoing radiotherapy. Integrating a yoga program into the treatment regimen of womenundergoing radiotherapy for breast cancer makes participation in the program easy andcompliance has been high. We will determine the efficacy of implementing a yoga program forpatients with breast cancer as an adjuvant to their radiotherapy. Patients with breast cancerwho are undergoing radiotherapy will be randomly assigned to one of three groups: a yogagroup, a stretching/relaxation group, or a waitlist control group. Participants in the twointervention groups will attend sessions 3 days/week throughout their 6-week radiotherapyschedule. Measures will be obtained prior to randomization, midway through radiotherapy,during the last week of radiotherapy, and 1 and 3, 6 and 12 months after the end ofradiotherapy. We will examine indices of QOL, fatigue, sleep disturbances, mental health, cost-effectiveness analysis, work and/or home productivity, and cortisol rhythmicity. We hypothesizethat the yoga program will help facilitate recovery and alleviate the physiological andpsychological side effects experienced by patients who are currently receiving radiotherapy.