On June 13, 2003 a 6 year old intact female beagle, "Molly", presented with the major complaint of buphthalmia and red eye. She was previously diagnosed and treated by her veterinarian for glaucoma. She was referred to Cornell for further examination. After an ophthalmic examination, Molly was diagnosed with hyperviscosity syndrome. Hyperviscosity syndrome is a rare condition associated with an increase in the concentration of macroglobulins in the blood. There are various manifestations of hyperviscosity syndrome with paraproteinaemicus retinopathy (tortuous, distended retinal veins) being pathognomonic. Other manifestations of hyperviscosity syndrome are hemorrhaging, especially retinal and gastrointestinal, visual defects, and neurologic deficits. Causes of hyperviscosity syndrome include multiple myeloma, chronic lymphocytic leukemia, primary (Waldenstrom's) macroglobulinemia, and lymphosarcoma with monoclonal elaboration of IgM, IgA, and IgG immunoglobulin and light chain protein classes. After an extensive diagnostic work up it was determined that Molly had a IgM secreting lymphoma of possible B-cell origin. Hyperviscosity is treated by reducing serum viscosity. This is best accomplished by treating the primary disease. Appropriate chemotherapy for Molly's lymphoma consists of the CHOP protocol which consists of L-asparaginase, prednisone, doxorubicin, cyclophosphamide, and vincristine. This would have been the most optimal treatment for this dog. However, the owner elected to forgo expensive chemotherapy and treat Molly with a pallative course of prednisone.