A 14 year old male castrated domestic longhaired cat was evaluated by the Cornell University Hospital for Animals' Emergency Service for an acute episode of reported open mouthed breathing, unresponsiveness and lateral recumbency. Abnormalities on presentation included dull mentation, nonambulatory tetra paresis, dehydration, anemia, hypoproteinemia and respiratory acidosis. While in hospital, a single episode ofhematemesis occurred, and subsequently clotting times were determined to be severely prolonged (PT and PTT). The abnormalities can be grouped together under a consolidated problem list including hypovolemic/distributive shock and hematemesis. Stabilization treatments were employed, including IV crystalloids, mannitol, fresh frozen plasma, anti-emetic and antacid. An abdominal ultrasound was performed, which revealed masses within the stomach, jejunum and colon, as well as gastric lymphadenopathy. Aspiration of the colonic mass was yielded a diagnosis of a mast cell tumor. The patient was started on prednisolone, omeprazole, famotidine and cyproheptadine. Once his anemia had stabilized, lomustine (CCNU) was administered as the sole chemotherapeutic agent for treatment of his gastrointestinal mast cell tumors. Fourteen weeks aher his first dose oflomustine, the patient was determined to be in complete remission. This paper will review differential diagnoses for hematemesis, as well as discuss the goals of medical management in feline patients with intestinal mast cell tumors.