Prostate cancer is the second most common cause of cancer death in American men. What to do when prostate cancer recurs months or years after a patient undergoes radical prostatectomy is an area of active research. Patients who underwent radical prostatectomy without immediate adjuvant radiation therapy (ART) but subsequently have evidence of recurrent disease are candidates for Salvage Radiation Therapy (SRT). Though there are three prospective randomized trials illustrating the efficacy of post-operative ART for selected patients, similarly strong evidence is lacking for SRT. In this article, we define the biochemical recurrence of prostate cancer, distinguish SRT from ART, outline the evidence for SRT, and make recommendations with regard to radiotherapy volume and dose. We discuss the known side effects from SRT, weigh the cost and benefit of SRT, and discuss possible tools that may improve the cost/benefit ratio for SRT by helping to select patients whom SRT may be more likely to benefit.