Canine and feline lymphoma is a common hematopoietic malignancy that generally responds well to systemic chemotherapy. In dogs, several recent investigations have underscored the beneficial effects of adjunctive radiation therapy for the treatment of multicentric lymphoma. With the emergence of effective immunotherapeutic agents against non-Hodgkin's lymphoma in people, some of these specific targeted immunotherapeutics may soon be a viable option for treating lymphoid malignancies in dogs. Although the effective and durable treatment of feline lymphoma remains disappointing, the identification of environmental etiologic factors may help to shape future recommendations for disease prevention. It is only reasonable to assume that as our fundamental understanding of lymphoid malignancies grows, better diagnostic tools, predictive markers, and therapeutic options will also emerge.