Faced with a rapid increase in health expenditure, advancing a high-value healthcare system is essential in developed countries. However, not all healthcare services provided to patients are valuable or lead to improved health outcomes. In the United States, unnecessary health care, including administrative waste and low-value care (healthcare services with little or no health benefit relative to cost), is estimated to account for 20% to 30% of total healthcare spending. Physicians are increasingly expected to provide high-quality, evidence-based care based on professionalism. A global movement to reduce unnecessary care and improve the value of health systems has been observed, like the Choosing Wisely initiative launched in 2012 by the American Board of Internal Medicine to identify commonly used low-value care service. To reduce unnecessary care and improve the value of care, it is imperative for policymakers, payers, and clinical leaders to understand how much society is spending on low-value care and whether this can be reduced. Studies based in the United States have reported that about 40% of Medicare beneficiaries receive some form of low-value care. However, international comparisons of use and spending on low-value care have been scarce. Building a common target built based on international comparisons will help advance the global initiative to reduce unnecessary care. In this context, I propose comparing use and spending on low-value care in Japan and the United States because they have contrasting healthcare systems that can affect the delivery of low-value care (i.e., different health insurance, hospital reimbursement systems, and drug pricing systems). First, I will construct a list of low-value care services applicable to claims databases in both Japan and the United States based on items specified by a multispecialty expert physician panel according to evidence-based medical literature (using an approach based on previous work). Second, I will examine the use and spending on the listed low-value care services. For Japan, the analyses will be conducted using nationwide insurance claims data from the National Database of Health Insurance Claims and Specific Health Checkups of Japan (NDB) Open Data for Japan. For the United States, they will be conducted using claims data from the Centers for Medicare and Medicaid Services (CMS) for the United States. These are arguably the best data to study this topic due to their accuracy, exhaustiveness, and representativeness. Finally, the results are compared between Japan and the United States regarding the 1) use/spending of low-value care per capita, 2) proportion of low-value care to total health care, 3) geographical variation of low-value care, and 4) details of low-value care. This project is highly policy relevant, contemporary, and comparative because it will underscore the underlying reasons and budgetary effects of the structure of low-value services in Japan and the United States and identify a common target to advance the ongoing global initiative to reduce unnecessary care. Given the urgent need to promote high-value healthcare systems, the current project matches well with the Abe Fellowship's mission – to encourage international multidisciplinary research on topics of pressing global concern.