Graduate School of Public Health, Seoul National University The national health insurance system in Korea is characterized as relatively high out-of-pocket payments, which are the principal source of catastrophic health expenditure (CHE). The objectives of this study are to estimate the incidence of household CHE and to clarify the characteristics that affect the occurrence and recurrence of household CHE using the Seoul Welfare Panel Survey database for 2008 and 2010. Thresholds to estimate CHE were 10% and 20% of the total household income (T/X), and 25% and 40% of the income excluding food share (T/Y). Determinants of the occurrence and recurrence of CHE at the threshold of T/X=10% were analysed using multiple logistic regression models. Out of the 3,665 households that responded in 2008 survey, households with CHE were 12.07% (T/X${geq}$10%), 5.34% (T/X${geq}$20%), 6.84% (T/Y${geq}$25%), and 4.44% (T/Y${geq}$40%). Risk factors associated with household CHE included living with a spouse, non-Medicaid beneficiary, householder unemployment, low household income, the number of disabled members, poor subjective health, and the number of chronic diseases. A total of 41.78% of households with CHE in 2008 repeatedly experienced CHE in 2010. Risk factors of CHE recurrence included decreased household income and an increase in chronic diseases over the two time periods, the number of members with disability or chronic diseases, and the presence of cancer patients in 2008. Households with lower socioeconomic and health status had a higher financial burden on health care than do their counterpart households. There is a need to enhance society-wide financial protection from health spending among vulnerable citizens in Seoul, particularly, households with low income, disabled members or cancer patients.