The objective of this study was to evaluate and compare the safety, tolerability and immunogenicity for two seasonal influenza subunit vaccines, one with MF59 adjuvant (Fluad) and one without an adjuvant (Agrippal). A total of 195 subjects aged > or = 65 years were enrolled to receive one dose of vaccine intramuscularly, 96 were vaccinated with Fluad, 99 received Agrippal. Blood samples were taken from all subjects in order to assess their antibody titre by the haemagglutination inhibition assay (HI), before (Time 0) and after (Time 1: 28 +/- 7 days) vaccination, against the A/H3N2 (A/Moscow/10/99), A/H1N1 (A/New Caledonia/20/99) and B/Shandong/7/97 antigens contained in the influenza vaccine in the 2002/2003 influenza season for the northern hemisphere. A good humoral antibody response was detected for both vaccines, meeting all the criteria of EMEA. The number of subjects in whom > or = 4-fold increase in antibody titre was recorded, in comparison with the pre-vaccination value, proved to be lower in the group vaccinated with AgrippaPl than in those vaccinated with the adjuvated preparation. Fluad" exhibited better immunogenicity than Agrippal. This difference was probably linked to the potentiated immune stimulation exerted by the adjuvant molecules. These results take on a particular importance if we consider that the immune system is weaker in the elderly; the administration of an adjuvated vaccine in such subjects is clearly preferable in that it provides greater and more prolonged protection. Both vaccines were generally well tolerated; no severe adverse events occurred in any of the subjects vaccinated, confirming the excellent safety profile of Fluad and Agrippal.