Hydrogel spacer placement between the prostate and rectum in men scheduled to undergo prostate radiotherapy is an emerging technique well suited for urologists. The hydrogel spacer reduces rectal injury during radiotherapy by displacing the rectum away from the high dose region. Following radiotherapy the hydrogel spacer then liquifies, is absorbed, and then clears via renal filtration in approximately 6 months. Herein we describe the appropriate patients eligible for this procedure, and the application technique we use in our clinic.