OBJECTIVE: To determine the impacts of out-of-pocket (OOP) health payments on household economic status before and after an implementation of the universal health care coverage (UC) policy in Thailand. METHODS: Analysis of socio-economic surveys on consumption expenditures of national representatives of households during 2000 (N=24,747), 2002 (N=34,785) and 2004 (N=34,843). RESULTS: Proportion of households whose OOP payments for health care deemed catastrophic (i.e., above 10% of total consumption expenditure) reduced from 5.4% in 2000 (pre-UC period) to 3.3 and 2.8% in 2002 and 2004 (post-UC periods), respectively. For the beneficiaries of Low-Income Card (LIC) and Voluntary Health Card (VHC) schemes, the health care catastrophe appeared in 4.7% of the households during the pre-UC period. The catastrophic incidence reduced to 3.2% and 2.6% among the UC beneficiaries during the post-UC periods. The percentage of households impoverished by the OOP health payments reduced after the UC implementation, from 4.4% in 2000 to 2.5% and 1.8% in 2002 and 2004. The post-OOP poverty incidence among the poorest quintile households reduced substantially from 18.3% to 10.3% and 8.0% over the same periods. An increase in the poverty headcounts (using national poverty line) as a result of OOP payments dropped from 2.1 percentage points during the pre-UC period to 0.8 and 0.5 percentage points during the post-UC periods. For the post-OOP impoverished households, an increase in the poverty gap reduced slightly from 0.7 percentage points in 2000 to 0.4 and 0.2 percentage points in 2002-2004. CONCLUSIONS: Reduction in the health care catastrophe and household impoverishment due to OOP payments is evident after the implementation of UC policy that provides comprehensive coverage of health care with a very small nominal fee of 30 Baht (or 0.75 USD) upon a visit or admission to health care facility for a comprehensive range of health services.