OBJECTIVES: Routine vaccination against influenza is recommended for all people aged 65 years or more. Without active encouragement to receive the vaccine, the rate of compliance is generally low. A study was undertaken to assess and compare the effectiveness of two reminder systems in improving the influenza vaccination rate. METHODS: A total of 2,017 patients aged 65 or over in a tertiary care hospital family practice center were randomly assigned to a control, a telephone reminder, or a postcard reminder group before the influenza season in 1998. The outcome measure, receipt of vaccination, was determined by telephone interview. Demographic and clinical characteristics were checked through the medical chart review. RESULTS: Among the 1,312 patients who actually received reminders and interviewed, the vaccination rate was 46.7% in the control group, 56.3% in the postcard reminder group, and 63.3% in the telephone reminder group. Vaccination compliance was significantly higher in people reminded by telephone (Odds ratio [OR], 2.00; 95% confidence interval [CI], 1.52-2.64) and postcard (OR, 1.55; 95% CI, 1.18-2.02) compared to that in the control group. Of the characteristics investigated, number of high risk co-morbidity was positively associated with vaccination compliance while current smoking was negatively associated. CONCLUSIONS: This result suggests that telephone and postcard reminders can significantly improve compliance with influenza vaccination in this group of Korean elderly. However, additional strategies need to be developed to encourage vaccination among noncompliant.