Background: Opisthorchis viverrini (OV) infection is the main risk factor for cholangiocarcinoma and is often found in Northeastern Thailand. The prevalence of OV infection and the incidence of cholangiocarcinoma are major public health problems in this region. Objectives: The objectives of this study were to identify factors associated with OV infection among people in Nong Khai Province in order to develop a prevention programme in the community. Materials and Methods: The data were collected in July 2013. Stool specimens were examined for intestinal parasites within hours after collection using a normal saline wet preparation and the modified KatoKatz technique. A case-control study was conducted to collect information about demographic data, the habit of eating unsafely prepared fish, the safe disposal of waste food, and the practice of defaecating in fields.