Rabies antibody titers ranged from 0-9.3 IU/mL in 117 human volunteers one year after intradermal vaccination with one or two doses of human diploid cell rabies vaccine (HDCV). At that time, each volunteer received one 0.1-mL booster dose of HDCV intradermally. All 117 volunteers showed good anamnestic responses, with antibody titers rising to 0.5-54.3 IU/mL within seven days of booster injection. Vaccine safety was good; only minor reactions were experienced, all of which resolved spontaneously.