An eleven-year old intact male Golden Retriever presented to the Oncology Service at Cornell University Hospital for Animals after chronic loss of appetite, lethargy, and profuse watery diarrhea. A large mass was noted on abdominal palpation at the referring veterinarian which was associated with the small intestine on ultrasound. On presentation he was quiet, dehydrated and in very thin body condition. A firm mid-abdominal mass was confirmed on palpation. An abdominal ultrasound revealed peritoneal effusion, diffuse thickening of the small intestinal wall, a discrete circumferential mass in the small intestine wall and an enlarged cluster of jejunal lymph nodes. Analysis of the peritoneal fluid and enlarged jejunal lymph nodes was consistent with T-cell lymphoma. Mild hypoalbuminemia was seen on a serum biochemical profile. The patient was stabilized with supportive care and started on a doxorubicin based multi-drug chemotherapy protocol. He was discharged to the care of his owners six days after admission with an improved appetite and energy level. On week three of his protocol he received doxorubicin. Two days later he became anorexic and had profuse diarrhea. He was admitted to the Oncology Service for supportive care. After two days of minimal improvement in his status his owners elected to euthanize due to poor prognosis. A necropsy was performed by the Pathology Service at Cornell University Hospital for Animals.