The purpose of this article is to present an updated set of American College of Radiology consensus guidelines formed from an expert panel on the appropriate use of radiation therapy in postprostatectomy prostate cancer. The American College of Radiology Appropriateness Criteria are evidence-based guidelines for specific clinical conditions that are reviewed every 3 years by a multidisciplinary expert panel. The guideline development and review include an extensive analysis of current medical literature from peer-reviewed journals and the application of a well-established consensus methodology (modified Delphi) to rate the appropriateness of imaging and treatment procedures by the panel. In those instances where evidence is lacking or not definitive, expert opinion may be used to recommend imaging or treatment. Recent and relevant literature reviewed by the panel led to establishment of criteria for appropriate use of radiation therapy in postprostatectomy prostate cancer. The discussion includes treatment technique, appropriate dose, field design, and the role of prostate-specific antigen (PSA). Ratings and commentary of the panel on multiple treatment parameters were used to reach consensus. Patients with high-risk pathologic features benefit from postprostatectomy radiation therapy.