A 5 year old Holstein cow presented to Cornell's Large Animal Medicine Service with a chief complaint of anorexia, depression, and decreased milk production. Abnormalities detected during physical examination and initial diagnostic evaluation included an abomasal mass, enlarged lymph nodes, and a lymphocytosis. A presumptive diagnosis of enzootic lymphoma was made, which was confirmed by the presence of lymphoblasts within a sample of peritoneal fluid obtained via abdominocentesis. The cow was euthanized, and both gross and histologic findings were consistent with the clinical diagnosis of lymphoma. Bovine enzootic lymphoma will be discussed with an emphasis placed on the bovine leukosis virus.