BACKGROUND: Controversy exists as to the criteria for selecting patients with carcinoma of the tonsil for treatment with ipsilateral radiotherapy (RT). METHODS: The American College of Radiology (ACR) Appropriateness Criteria are evidence-based guidelines for specific clinical conditions that are reviewed every 2 years by a multidisciplinary expert panel. The guideline development and review include an extensive analysis of current literature from peer reviewed journals and the application of a well-established consensus methodology (modified Delphi) to rate the appropriateness of treatment procedures by the panel. In those instances where evidence is not definitive, expert opinion may be used to recommend treatment. RESULTS: The ACR Expert Panel on Radiation Oncology - Head and Neck Cancer developed consensus recommendations for selecting patients with tonsillar carcinoma for ipsilateral RT. CONCLUSION: Patients that are appropriate for ipsilateral RT have less than 1 cm of tumor invasion into the soft palate or base of tongue, and nodal stage of N0 to 1.