Meningococcal serogroups A and C cause significant numbers of cases in China. The Sanofi Pasteur Men-AC was licensed in China in 1995. Immunogenicity and safety of a single dose of Men-AC against a similar marketed vaccine, the Lanzhou Institute serogroups A and C vaccine, were evaluated in children 2 to 6 years of age. Antibody titers were determined before and on Day 30 after vaccination using a serum bactericidal assay using baby rabbit complement. Immunogenicity endpoints included rates of seroconversion and seroprotection. Unsolicited systemic AEs within 30 minutes after vaccination, solicited injection site and systemic reactions between Days 0 and 7, unsolicited non-serious AEs within 30 d, and Researchers recorded severe adverse events throughout. Seroconversion rates against serogroups A and C were 97.0% and 94.7%, respectively, in the Men-AC group and 97.7% and 94.8%, respectively, in the Lanzhou-AC group, while seroprotection rates were 98.0% and 97.0%, respectively, in the Men-AC group and 99.0% and 96.8%, respectively, in the Lanzhou-AC group. Non-inferiority of Men-AC concerning immunogenicity was demonstrated since the lower bounds of the 95% CIs of the differences in rates between the two groups were > −5% for both serogroups. Both vaccines were well tolerated.