Chestnut Blight is an introduced disease in Portugal associated with virulent strains of the Asian fungus Cryphonectria parasitica (Murril) Barr. The disease causes great economic losses and presents a significant risk to the chestnut ecosystem. Eradication efforts and cultural sanitary measures didn’t control the disease and actually more than 10% of chestnut trees are blighted. A new method based on hypovirulence was achieved and a program for biological control of Chestnut Blight was implemented for field extended application. The program is a transfer initiative that encourages the application of Hypovirus CHV-1 strains as a component of the integrated management of the disease. Hypovirus CHV-1 strains were timely approved by national authorities (Ministry of Agriculture-DGAV) and stakeholders and schedules of field applications implemented. General achievements and results of the program will be presented and evaluated.