How best to provide effective protection for the poorest against the financial risks of ill health remains an unanswered policy question. Community-based health insurance (CBHI) schemes, by pooling risks and resources, can in principal offer protection against the risk of medical expenses, and make accessible health care services that would otherwise be unaffordable. The purpose of this paper is to measure the distributional impact of a large CBHI scheme in Gujarat, India, which reimburses hospitalization costs, and to identify barriers to optimal distributional impact. The study found that the Vimo Self-employed Women's Association (SEWA) scheme is inclusive of the poorest, with 32% of rural members, and 40% of urban members, drawn from households below the 30th percentile of socio-economic status. Submission of claims for inpatient care is equitable in Ahmedabad City, but inequitable in rural areas. The financially better off in rural areas are significantly more likely to submit claims than are the poorest, and men are significantly more likely to submit claims than women. Members living in areas that have better access to health care submit more claims than those living in remote areas. A variety of factors prevent the poorest in rural and remote areas from accessing inpatient care or from submitting a claim. The study concludes that even a well-intentioned scheme may have an undesirable distributional impact, particularly if: (1) the scheme does not address the major barriers to accessing (inpatient) health care; and (2) the process of seeking reimbursement under the scheme is burdensome for the poor. Design and implementation of an equitable scheme must involve: a careful assessment of barriers to health care seeking; interventions to address the main barriers; and reimbursement requiring minimum paperwork and at the time/place of service utilization.