An investigation of the helminth parasites of house rat R. norvegicus Erxl. in Seoul has been carried on four years. A total of 325 rat was examined. Ten species of helminths were considered, of which 4 species were recored for the first time from Korea. The adult worm of Capillaria hepatica, the most common parasite of house rats in Seoul, was observed experimentally, and provided a more complete description of this worm.
