Activity-based financing (that is, casemix-based hospital payments, known as T2A) is intended to harmonize and improve the fairness of remuneration of public and private hospitals. T2A will ultimately rely mainly on a flat rate per admission, set according to the diagnosis-related group (DRG). Although payment for drugs is usually included in the DRG price, some expensive drugs will be reimbursed on an additional cost basis after implementation of a "best practices" agreement. Four drugs used for treatment of pulmonary arterial hypertension are eligible for this additional reimbursement: 3 prostacyclin derivatives (intravenous epoprostenol, inhaled iloprost, and subcutaneous treprostinil), and oral bosentan, an endothelin receptor antagonist. The Pulmonary Vascular Diseases working group of the French Society of Pulmonary Medicine has developed guidelines for the best practices in use of these drugs.