Bovine viral leukosis is a viral disease of cattle characterized by the development of tumors in the lymphatic tissue. A female Holstein, 3-year-old, was submitted for diagnosis at the Diagnostic laboratory, Chonbuk National University. Clinical sign of the affected animal showed emaciation, enlargement of superficial lymph node and mild diarrhea. Remarkable lesions were enlargement of many internal lymph nodes. Histopathology revealed excessive neoplastic lymphoid cells characteristic of BVL infection. Subsequently, serums from all cattle were collected and serological examination was done where a 85% seropositive rate was detected using ELISA test. ELISA method showed a comparatively 75% higher detection rate than the agar gel immunodiffusion (AGID) test (85% vs 40%). Serologically positive cattle were variably detected in all ages from under 1 year to over 6 year of age. Hematological examination consistently showed leukocytosis and a differential lymphocytosis of seropositive cattle. Detailed comparative pathological and serological data diagnosed the presence of bovine viral leukosis.