Household survey data from China is used to analyze the determinants of households' willingness to pay to participate in the New Cooperative Medical System (NCMS). Wealthier households, households with at least one member who has been treated as an inpatient, and households in counties where NCMS is already established are willing to pay more for the program. Households who carry other forms of insurance, however, have a lower willingness to pay for the NCMS. We also find that the participation fee could be increased substantially to increase the size of the risk pool while scarcely affecting participation rates. (JEL I1, O1, D1)