During May-July, 1978 a survey on the prevalence of C. hepatica among house rat(Rattus norvegicus Erxl.) and wild mice (Mus musailus molossinus and Microtus mandarinus) in two districts in Seoul was carried out. Approximately 38 percent of 1,000 house rats examined were infected. Rat population as an established group in Ahyundong, neighbouring the city, revealed 39.2 percent of infection among 660 house rats, and that as newly formed group in Shinrimdong, a developing residential quarter on the southern outskirts of Seoul showed 35.9 percent among 340 rats. Infection rate of females and males was 38.9 percent and 37.2 percent respectively. Differences of infection rates by locality and sex were not statistically significant. It was very interesting that none of 64 wild mice were infected with this parasite in both districts. Some probable factors which are related on C. hepatica infection among rats were discussed briefly.
