The benefit of annually repeated influenza vaccination on antibody formation is still under debate. In this study the effect of annually repeated influenza vaccination on haemagglutination inhibiting (HI) antibody formation in the elderly is investigated. Between 1990 and 1993 healthy young and elderly, both selected by the SENIEUR protocol, were vaccinated consecutively with commercially available influenza vaccines. The elderly had a lower HI antibody response after one vaccination as compared to the young against the A/Taiwan/1/86 (HINI), B/Yamagata/16/88 and B/Panama/45/90 strains. Annually repeated vaccination did not result in a decrease of the HI antibody titres against the A and B vaccine strains in both age groups. Moreover, the elderly had a significantly higher HI titre against the B strains after the second vaccination as compared to the first, resulting in comparable HI titres for young and elderly. Thus, annually repeated vaccination has a beneficial effect on the antibody titre against influenza virus and can contribute to a better antibody-response in the elderly.