This study was carried out a survey for the presence of Giardia intestinalis infections in dogs using a Giardia ELISA kit (SNAP) test, IDEXX Laboratories, Inc., Westbrook, ME). Four hundred and seventy-two dogs (190 males and 282 females) were examined for a G. intestinalis infection in four different provinces (Kyunggi, Chonnam, Kyungnam and Chungnam) and a Seoul city in South Korea. Slightly more male dogs (15.0%) than female (8.6%) dogs were affected, there was no significant difference between the two groups. The overall positive rates of G. intestinalis infection were 11.2%, 14.9% being found in the <2-year-old group, 8.7% in the 2-5 year-old group, and 2.1% in the >5-year-old group. X(2) analysis revealed a significantly higher prevalence (14.9%, P<0.05) in the <2-year-old group than in the other two groups, and a significantly higher prevalence in symptomatic dogs (47.6%, P<0.001) in asymptomatic dogs (7.7%). This study is the first large-scale survey of canine G. intestinalis infections in South Korea, and is expected provide a useful reference for clinicians. Giardia-infected dogs should be treated for hygienic management as well as to prevent dog to human transmission.