From 1988 to 1992, 2479 volunteers were immunized by inactivated Meriones unguiculatus kidney cell (MUKC) vaccine. Their seroconversion rates of neutralizing antibody were about 90% after 3 doses of the vaccine. No side effects were found. The vaccine stored for 14 months at 4 degrees C still had good immunogenicity. It was shown that the vaccine was safe, effective and stable. Detailed observation was made in 75 volunteers. The results showed that the seroconversion rate by plaque reduction neutralization test in 3 doses group was higher than that in 2 doses group; but the results by reversed passive hemagglutination (RPHI), immunofluorescence assay (IFA) and ELISA were similar. Different immunization procedures (3 x 1 ml during 28 days or 3 x 1 ml during 60 days), injection routes (im or sc) and vaccine forms (containing adjuvants or not) showed no significant difference. If secondary immunization (one dose) was given one year after primary immunization, geometric mean titre of the neutralizing antibody was two fold higher than that after primary immunization.