As policymakers consider whether and how to add prescription drug coverage to Medicare, they need to understand the relationship between insurance coverage and the adoption of new medical technologies, including drugs. Even the direction of these relationships is not always so clear. In this Issue Brief, Drs. Danzon and Pauly examine the shift from inpatient to outpatient care in the last 20 years, and ask two broad questions: to what extent was this shift encouraged by changes in insurance, and to what extent was insurance coverage influenced by this shift?