The veterinary oncology profession is uniquely able to contribute to the many advances that are imminent in immunotherapy. However, what works in a mouse will often not reflect the outcome in human patients with cancer. Therefore, comparative immunotherapy studies using veterinary patients may be better able to bridge murine and human studies. Many cancers in dogs and cats seem to be stronger models for their counterpart human tumors than presently available murine model systems. This author looks forward to the time when immunotherapy plays a significant role in the treatment and/or prevention of cancer in human and veterinary patients.