User fees in health services are a source of much debate because of their potential risk of negative effects on access to health care for the poor. A Health Equity Fund that identifies the poor and pays on their behalf may be an alternative to generally ineffective fee exemption policies. This paper presents the experience of such a Health Equity Fund, managed by a local non-governmental organization, in Sotnikum, Cambodia. It describes the results of the first 2 years of operations, investigates the constraints to equitable access to the district hospital and the effects of the Health Equity Fund on these constraints. The Health Equity Fund supported 16% of hospitalized patients. We found four major constraints to access: financial, geographical, informational and intra-household. The results of the study show that the Health Equity Fund effectively improves financial access for the poor, but that the poor continue to face many constraints for timely access. The study also found that the Health Equity Fund as set up in Sotnikum was very cost-effective, with minimal leakage to non-poor. Health Equity Funds managed by a local non-governmental organization seem to constitute a promising channel for donors who want to invest in poverty reduction. However, further research and experimentation are recommended in different contexts and with different set-ups.