BACKGROUND Influenza is responsible for significant morbidity, mortality, and medical costs, but immunization rates in the elderly remain low. METHODS As part of a demonstration project in rural Pennsylvania, 1,989 community-dwelling Medicare beneficiaries, 65-79 years old, completed a health risk appraisal including questions about flu shots. Participants were randomized to two experimental (hospital or physician) or control groups. Experimental groups were offered free flu shots for the 1990-91 flu season. Follow-up interviews to determine vaccination rates were completed about 1 year later. RESULTS Baseline immunization rates were almost identical for the hospital-based (41.2%), physician-based (41.3%), and control group not offered free immunizations (40.6%). Follow-up rates for the groups offered immunizations rose significantly to 63.6 and 69.1% for hospital and physician groups, respectively, while the control group also increased significantly to 54.1%. Individuals who were more educated, were older, and had greater chronic diseases history (myocardial infarction, hypertension, and pulmonary disease) were more likely to be immunized. Male and married elderly were more likely to be immunized as a result of the demonstration. CONCLUSIONS Increasing community education and providing immunizations free through Medicare will increase immunization rates among elderly. The elderly are more likely to receive flu shots provided through physicians' offices than through hospital-based clinics.