To document how out-of-pocket health expenditure can lead to debt in a poor rural area in Cambodia. After a dengue epidemic, 72 households with a dengue patient were interviewed to document health-seeking behaviour, out-of-pocket expenditure, and how they financed such expenditure. One year later, a follow-up visit investigated how the 26 households with an initial debt had coped with it. The amount of out-of-pocket health expenditure depended mostly on where households sought care. Those who had used exclusively private providers paid on average US dollars 103; those who combined private and public providers paid US dollars 32, and those who used only the public hospital US dollars 8. The households used a combination of savings, selling consumables, selling assets and borrowing money to finance this expenditure. One year later, most families with initial debts had been unable to settle these debts, and continued to pay high interest rates (range between 2.5 and 15% per month). Several households had to sell their land. In Cambodia, even relatively modest out-of-pocket health expenditure frequently causes indebtedness and can lead to poverty. A credible and accessible public health system is needed to prevent catastrophic health expenditure, and to allow for other strategies, such as safety nets for the poor, to be fully effective.