Naturally-occurring cancers in pet animals are becoming increasingly recognized as an opportunity to advance studies in cancer drug and therapeutic development. The field of comparative oncology studies and treats canine and feline cancers both for therapeutic intent in the animal itself as well as a research tool to further understanding of human cancer and cancer therapies. This symposium will provide an introduction to the field of comparative oncology through discussions of the mutational landscape and driver mutations present in canine cancers, and how therapeutic trials in pet dogs can generate pharmacodynamic and pharmacokinetic information beneficial to the drug development process.