Physicians dealing with potential rabies exposures and travel medicine are frequently asked how long previous pre- or post-exposure rabies vaccination induced immunity persists. We therefore carried out a prospective study on 118 rabies vaccine recipients who had received pre- or post-exposure regimens with tissue culture rabies vaccines by intramuscular or intradermal schedules 5-21 years previously. Rabies neutralizing antibody was detectable in the sera of all subjects on day 0. They then received one intradermal 0.1 mL booster injection on days 0 and 3. Neutralizing antibody determination was carried out on days 5, 7 and 14. All except one subject showed an accelerated antibody response following the two booster injections. Vaccination with a WHO recognized tissue culture rabies vaccine evokes long lasting immunity. This study supports current recommendations that immunity is long lasting and that boosters without immunoglobulin are sufficient even when prior vaccination was longer than 5 years previously.