Immune responses to trivalent inactivated whole virus and monovalent subunit influenza vaccines, used in the season 1986-87, were analyzed in elderly residents in nursing homes. Higher levels of induced antibody were found in the group receiving two doses of trivalent vaccine. This suggests that high risk aged patients should receive a booster dose of vaccine annually. The antibody response to administration of supplemental vaccination, using monovalent subunit preparation, did not reach the high level of antibodies found following trivalent influenza vaccine.