Continuous low‐dose‐rate irradiation of animal tumors has become feasible through the implantation of iridium‐192 by an afterloading technique. 192Ir is an ideal radioisotope for interstitial brachytherapy in veterinary medicine because of its 74.2‐day half‐life, medium‐energy gamma radiation (0.35 MeV), moderate shielding requirements, low cost, and adaptability to most tumor configurations. The afterloading technique can easily be applied to veterinary patients. The effectiveness of interstitial brachytherapy may be enhanced by combination with surgery and/or hyperthermia. Computer‐assisted dose calculations make afterloaded 192Ir implantation an accurate, precise method of interstitial brachytherapy.