The health insurance card scheme wasintroduced as the Health Card Project (HCP) in 1983. Thisprogram was based on the risk sharing of health expenditureswith no cost sharing in a voluntary health insuranceprepayment scheme. Frequent adjustments in both thestrategies and objectives of the program have includedvoluntary risk sharing with cost recovery in addition toservice provision. The HCP needs a large enough number ofenrollees to ensure a sufficient pool of risks. However, thenewly elected government of Thailand has committed torapidly extending health care coverage to all Thai citizens.Even though the HCP was suppressed and replaced by thisprogram in October 2001, this study of the determinants ofdemand for the prepaid health card is still important. TheHCP can be assessed as relatively progressive, serving ruralareas, poor and near poor groups. This study has found thatemployment, education, and the presence of illness aresignificant factors influencing card purchase. The thirdfactor is related to the problem of adverse selection of theprogram; families with symptoms of sickness are more likelyto buy cards and increase their use of health services. Theresults also show an improvement in accessibility to healthcare and a high level of satisfaction among cardholders,both key objectives of the program. Problems of programperformance include issues of program and financialmanagement: marketing, quality control and cost recovery;ineffective referral systems, and lack of limits on episodesand ceilings for expenses. There is a need for an efficientand consistent health policy, which would involve revisedcriteria for card use, standard reimbursement agreementswith hospitals, government subsidies, and an overallstrengthening of the program.