Two cases of classical swine fever (CSF) disease have broken out in Cheolwon (7 April, 2002). The suspected pig herds were huddled together because of high fever (over $40^{circ}C$) and showed remarkable decrease of the leukocytes. The staggering gait related to posterior weakness, constipation and lethargy, hyperemia, hemorrhagic lesions (on the skin, muzzle, ears, limbs, tail and inner part of legs) and conjunctivitis with dirty streaks below the eyes were observed. The inflammation in the lung, infarction in the spleen, swelling and hemorrhage in lymph nodes, kidney, intestine, heart and cheese like purulent inflammation of the tonsil were observed. The ulcers of the colon were also detected. Several clinical and laboratory techniques including blood test, histo-pathological examinations, indirect fluorescent antibody (IFA) test and RT-PCR test were applied to diagnose the disease. Inoculation test on PK-15 cell was also performed. The necrosis of the lymphatic cells and infiltration of the vessel circumferential cells in the brain and lymph organs were commonly viewed. The proliferation of the glia cell (gliosis) in the lymph was particular. Cytopathogenic effect (CPE) and specific fluorescent-bright-green areas (with IFA) appeared in PK-15 cells inoculated with suspected blood plasma. The IFA test on the epithelial and mucous membrane cells of tonsil was positive. RT-PCR technique required more working hours and labor than other techniques in this examination but it was useful because of the sensitivity to the CSF viral gene.