Background and Significance Asthma is one of the most common serious chronic diseases of adults and children in the United States. Despite guidelines and evidence, adherence to recommended asthma controller medications is low. Cost is an important barrier to non-adherence to asthma medications. Employers are increasingly adopting high-deductible health plans (HDHPs) particularly those that qualify for Health Savings Accounts (HSAs), which subject most medications to deductibles rather than copayments as in traditional coverage. HSA-HDHPs can thus lead to forgone care due to cost, including clinically appropriate services such as asthma medications. As a response, value-based insurance designs (VBID) have been proposed to promote high-value care by reducing or eliminating cost-sharing for these services. One common example is a Preventive Drug List (PDL) that can accompany HSA-HDHPs, which exempts certain chronic medications from the deductible to promote adherence. Many PDLs include asthma controller and rescue medications. With the increasing prevalence of HSA-HDHPs, PDLs have the potential to improve controller medication adherence for both adults and children.