here is little information about Korean children's secondhand smoke (SHS) exposure at home. This paper examines the extent and determinants of their SHS exposure at home. A population-based random digit dial telephone survey was conducted in 2002 with 500 adults in Seoul. We analyzed data for 207 adults with children living in the household. Thirty-one percent of respondents reported children' s SHS exposure at home. The mean weekly dose was 5 cigarettes among exposed children. Multiple logistic regression results showed that children's odds of SHS exposure at home increased if the respondent or spouse smoked, if the respondent's parent smoked, if smoking was allowed in the home, and if fewer groups discouraged smoking. Stronger protective measures are urged, such as widespread increase in home smoking bans and discouragement of smoking.