The aim of the report is to reviewexisting approaches and available policy options to improveaccess to health care services and financial protectionagainst health shocks for informal-sector workers (ISWs).Along with their families, ISWs represent the majority ofthe population in many developing countries. The reportreviews the definition and measurement of the informalsector and the literature on efforts toward its healthinsurance coverage. It also examines several country casesbased on published and unpublished reports and on structuredinterviews of expert informants. Developing country effortsto expand health coverage are characterized by a commonenrollment and financing pattern, starting withformal-sector workers and following withgovernment-subsidized enrollment of the poor. Thus, ISWs aretypically left behind and have been referred to as "themissing middle." They find themselves financiallyunprotected against health shocks and with limited access toquality and timely health care. ISWs are generally reluctantto enroll in insurance schemes, including social healthinsurance (SHI), community insurance, and otherarrangements. Further, initiatives to enroll them inself-financed contributory schemes have generally resultedin adverse selection, as those with high anticipated healthneeds are more willing to pay and enroll than others.Successful initiatives to cover this population group arethe ones where government has abandoned its expectations toderive relatively substantial revenue from it. Offering thisgroup a benefits package that is relatively smaller thanthat of formal workers and charging them a premium that isonly a fraction of that charged to formal workers is astrategy used by some countries to limit the need for publicsubsidies. While there is evidence that greater insurancecoverage has improved access to health services for ISWs andtheirdependents, in several countries it has not yetimproved financial protection for this target group. A broadset of reforms will be required to strengthen the supplyside to ensure that additional public financing translatesinto improved coverage for ISWs.