The safety, immunogenicity, and immunologic priming of 2 dosages (2 μg or 10 μg) of a meningococcal C oligosaccharide-CRM197 conjugate vaccine was evaluated in 114 infants vaccinated at ages 2, 3, and 4 months. Antibody persistence and response to boosting with 10 μg of meningococcal C polysaccharide were assessed. The meningococcal conjugate vaccine produced fewer local reactions than concurrent routine immunizations. Total serogroup C-specific immunoglobulin geometric mean concentration (GMC) increased from 0.3 μg/mL before vaccination to 13.1 μg/mL at age 5 months. Serum bactericidal antibody (SBA) geometric mean titers (GMTs) rose from <1:4 to 1:1057 at 5 months and fell by 14 months to 1: 19. Following boosting, anti- C-specific immunoglobulin GMC rose to 15.9 μg/mL and SBA GMT to 1:495. Antibody responses in the 10-μg dose cohort were significantly higher at 5 months (P < .01) than in the 2-μg dose cohort but were lower after polysaccharide boosting (P = .02). This meningococcal conjugate vaccine was well tolerated and immunogenic and induced immunologic memory in infants.