Background: $Clonorchis$ $sinensis$ is an important human parasite that is usually found in the biliary tract. It is widely distributed in East Asia in Taiwan, Japan, China and Korea. About 2 million people are estimated to be infected with $C.$ $sinensis$ in Korea. This study was conducted to evaluate the state of infestation and clinical aspects of $C.$ $sinensis$. Material and Methods: We evaluate 1,063 patients with clonorchiasis retrospectively at Yeungnam University Hospital and Health Promotion Center from January 2001 to December 2003. All patients were diagnosed by a positive stool test for $C.$ $sinensis$ eggs. Clinical features, laboratory data and imaging studies were evaluated. Results: The ratio between affected males and females was 3.6 : 1. The highest infection rate was noted in the 40-60 age groups regardless of sex. The infection rate of $C.$ $sinensis$ among the residents of urban areas was higher than in rural areas. There were 813 (76.5%) patients who were asymptomatic. Common symptoms included right upper abdominal pain in 7.6% and epigastric pain in 7.2%. For the laboratory studies, serum ALP and GGT levels were within normal limits in 85.2% and 56.0% respectively. Peripheral eosinophilia was noted in 66.1% of cases. Of the 83 cases undergoing ERCP, 27 cases (32.5%) showed peripheral dilatation of the intrahepatic duct. Conclusion: This study suggests that $C.$ $sinensis$ infection is still endemic even in rural areas of Korea and that asymptomatic infections are common. Further work should be focused on the early diagnosis and treatment of patients with subclinical infection.