A 12-year old neutered male Yorkshire terrier dog was presented to the Veterinary Medical Teaching Hospital of Seoul National University with a history of chronic intermittent diarrhea, vomiting, anorexia and weight loss of 2-months duration. On presentation, he was very cachexic and had ascites. Abnormal findings on a complete blood count and chemistry profile included mild anemia, leukocytosis, panhypoproteinemia, hypocholesterolemia, decreased blood urea nitrogen (BUN) and increased serum bile acids. Radiographic findings indicated microhepatica. Peritoneal fluid analysis was consistent with transudates (total protein < 2.5 g/dl, total nucleated cell count = 2,200/ul) and cytologic examination of the fluid revealed neoplastic lymphoblasts. From these findings hepatic dysfunction and protein-losing enteropathy were attributable to abdominal lymphoma. This case suggests that cytologic examination is important in diagnosing underlying diseases of ascites, even if it is transudative effusion.