OBJECTIVES: To explore the economic impact of high costs of renal replacement therapy (RRT) for end-stage renal disease (ESRD) patients, excluded from the UC benefit package on Thai households of different economic status. METHODS: In-depth case studies of twenty households, all with ESRD patients, were undertaken using three qualitative data collection approaches: semi-structured and in-depth interviews, and direct observation.  Poorer and richer households located in urban and rural areas of Nakorn Ratchasima province were purposively selected. Each household was regularly visited every two weeks for three months. Interviews were transcribed and analyzed using a thematic approach, and notes from direct observation were analyzed using content analysis. RESULTS: The decision to exclude RRT from the UC benefit package generated considerable financial barriers to access for, and a substantial economic impact on, poorer ESRD patients.  Infrequent access to RRT and inability to obtain essential and expensive injectable medication due to limited household resources appeared to be a major cause of death for poorer ESRD patients.  Health expenditure for RRT captured 25-68% of household income and 31-52 % of household expenditure, which meant that ESRD patients faced catastrophic health spending.  In contrast, richer ESRD patients could access and utilize RRT regularly and effectively, resulting in a higher survival rate and quality of life than their poorer counterparts. Various coping strategies were used by poorer ESRD patients to manage the high costs of RRT, including reducing the frequency of haemodialysis, reducing food consumption, using only public transportation, and taking loans with a high interest rate.  The cost burdens of RRT not only had economic impacts on ESRD patients, but also on their household members and relatives who provided financial support.  CONCLUSIONS: The catastrophic impact of RRT costs on poorer households calls into question the appropriateness of the UC benefit package and requires serious attention by the Thai government.