Classical swine fever(CSF) was confirmed in 19 herds in Jeunbuk provence(Iksan, Gimje, Wanju, Buan, and Jangsu) in Korea between March and May, 2003 and 10,263 pigs were slaughtered. Pigs contacted with CSF virus in primary outbreak farm show fever, reduced appetite, arched back and chill in company with sever respirative sign and then most infected farms also were observed to fever, reduced appetite, sudden death, and leukopenia(101 pigs). In order to detecting infectious pig with CSF virus, A total of 555 pigs were inspected in 65 herds and blood samples were collected and serological test(ELISA), antigen ELISA, and reverse transcription-polymerase chain reaction(RT-PCR) had been done. Positive rate were 74%(410 pigs) in antibody ELISA, 2%(11 pigs) in antigen ELISA and 33%(182 pigs) in RT-PCR, respectively. As shown that the RT-PCR was useful than the ELISA for determining CSF virus in blood, meat, and other organs.