Abstract: The purpose of this study was to assess risk for lymphedema of the breast and arm in radiotherapy patients in an era of less extensive axillary surgery. Breast cancer patients treated for cure were reviewed, with a minimum follow-up of 1.5 years from the end of treatment. Clinical, surgical, and radiation-related variables were tested for statistical association with arm and breast lymphedema using regression analyses, t-tests, and chi-squared analyses. Between January 1998 and June 2001, 240 women received radiation for localized breast cancer in our center. The incidence of lymphedema of the ipsilateral breast, arm, and combined (breast and arm) was 9.6%, 7.6%, and 1.8%, respectively, with a median follow-up of 27 months. For breast edema, t-test and multivariate analysis showed body mass index (BMI) to be significant (p = 0.043, p = 0.0038), as was chi-squared and multivariate testing for site of tumor in the breast (p = 0.0043, p = 0.0035). For arm edema, t-test and multivariate analyses showed the number of nodes removed to be significant (p = 0.0040, p = 0.0458); the size of the tumor was also significant by multivariate analyses (p = 0.0027). Tumor size appeared significant because a number of very large cancers failed locally and caused cancer-related obstructive lymphedema. In our center, even modern, limited level 1–2 axillary dissection and tangential irradiation carries the risk of arm lymphedema that would argue in favor of sentinel node biopsy. For breast edema, disruption of draining lymphatics by surgery and radiation with boost to the upper outer quadrant increased risk, especially for the obese. Fortunately both breast and arm edema benefited from manual lymphatic drainage.