In this study researchers will examine the initial efficacy of implementing a yoga program for patients with breast cancer as an adjuvant to their radiotherapy. Patients with breast cancer who are undergoing radiotherapy will be randomly assigned to either a yoga group (YG), or a stretching (ST) control group, or a waitlist control (WL) group. Participants in YG and ST groups will attend three sessions each week throughout their 6-week radiotherapy schedule. The sessions will be coordinated with the treatment schedule and conducted adjacent to the treatment facility. Measures will be obtained prior to randomization, a brief assessment during the middle of radiation therapy, during the last week of radiation therapy, and 1, 3 and 6 months after the last radiation session. With the inclusion of two control groups in this randomized trial researchers will attempt to validate the benefits of yoga as an adjuvant to radiotherapy in patients with breast cancer wherein researchers will control for specific components of the yoga program and also examine some of the mechanisms that are necessary for the program to be effective.