OBJECTIVES: To assess the impact of achieving universal coverage (UC) on equity in health care finance and on financial risk protection from expensive medical care costs for Thai households. METHODS: Secondary data analyses using nationally representative household surveys conducted by National Statistical Office, the Socio-economic Survey 2000 (prior to UC) and 2002-2006 (after UC) to analyze changes in progressivity of overall health care finance and different health financing sources.  The share of households facing catastrophic health expenditure in the poorest and richest income quintiles prior to and after achieving UC was also assessed. RESULTS: The financing of the Thai health care system became more equitable after the UC policy was implemented.  Improved financial risk protection after achieving UC was observed due to the comprehensive benefit package and literally free at point of services.  The Kakwani index value for overall health care finance changed from -0.0038 (regressive) in 2000 to positive (progressive) values of 0.0014, 0.0342 and 0.0406 in 2002, 2004 and 2006, respectively. The share of households facing catastrophic spending on health decreased from 5.4% in 2000 to 2.0% in 2006.  The 1st (poorest) quintile experienced a 77.5% reduction in the proportion of households facing catastrophic health expenditure, while there was a 41% reduction in the share of households in the 5th (richest) quintile.  CONCLUSIONS: Factors contributing to equitable health finance are: the increasing share of progressive financing sources in particular direct tax; the decreasing share of the regressive out-of-pocket payments for health.  Using general taxation to finance the poor and the informal sector not only helps reach universal coverage, it is also the most progressive financing source.  Various factors contribute to the low incidence of catastrophic heath expenditure: comprehensive benefit package covering almost all health services which are free at point of use, and well-functioning primary care providers.