The objective of this work was to develop a new delivery system which could enhance the mucosal immune response to influenza virus antigens. Poly(D,L-lactide-co-glycolide) nanoparticles of about 200 nm containing hemagglutinin were chosen as the delivery system. Due to the amphiphilic nature of hemagglutinin (hydrophilic HA1 and hydrophobic HA2), nanoparticles were prepared by both classical oil in water solvent evaporation technique as well as by a [(water-in-oil) in water] solvent evaporation technique. Hemagglutinin was well encapsulated in nanoparticles prepared by both techniques. Molecular weight and antigenicity of entrapped hemagglutinin were not affected by the entrapment procedure.