Despite the US Food and Drug Administration's approval in 1996, tissue plasminogen activator (tPA) therapy for acute ischemic stroke remains substantially underused. We reviewed 3 potential reasons for low rates of tPA use: poor patient education, physicians' perceived risk of legal liability from negative patient outcomes, and insufficient reimbursement. The recent addition of diagnosis-related grouping code 559 will provide higher payment for stroke patients treated with tPA, creating a natural experiment to examine our third reason.