OBJECTIVES:  Pulmonary Arterial Hypertension (PAH) is a rare disease, accompanied by severe morbidity, mortality and costs. Bosentan is the most widely used PAH treatment, especially in the moderate-severe stages of the disease. The purpose of this study was to estimate the potential budget impact of adopting generic bosentan for PAH therapy, in view of its introduction to the Greek setting. METHODS:  A budget impact model was developed over a 5-year time horizon. Epidemiological data, clinical inputs and disease management information were obtained from published literature plus expert opinion. Treatment strategies involved both supportive and specialized treatment. Cost parameters included medication costs, patient monitoring, inpatient costs, outpatient visits and adverse events and derived from official pricing (EOF) and reimbursement (EOPYY) lists. Outcomes of the analysis reflected total costs over the study horizon, under two scenarios: “world with” and “world without” generic bosentan. Penetration of generic bosentan was illustrated by a forecasted increase in Endothelin Receptor Antagonists (ERA) market shares. A third-party payer perspective was employed. RESULTS:  Total 5-year costs were estimated at €28,650,999 with the inclusion of generic bosentan in the PAH therapy mix and €31,134,401 otherwise, representing a 8.78% decrease. Total savings exceed the €2.5 million mark (€2,513,402) and reach a maximum of €837,944.5 for the 5^th year, with an average saving of €10,738.52 per patient (€2,147.70 annually). At an assumed budget of €2 million, opting for generic bosentan allows 23 more patients (115 vs 92) to receive treatment, at an annual basis. CONCLUSIONS:  The adoption of generic bosentan as a treatment option for PAH could result in significant budget savings for the Greek healthcare system, demonstrating the importance of optimal resource allocation in a rare disease.