This study evaluated the immunogenicity and reactogenicity of a group C meningococcal conjugate vaccine (MenC) compared with a group A+C meningococcal polysaccharide vaccine (MenPS) in healthy adolescents. Subjects were randomised to receive one dose of either MenC (n=92) or MenPS (n=90). Group C meningococcal IgG antibody concentrations and bactericidal titres were higher in the MenC group than the MenPS group at 1 month (22.8 U/ml vs 4.0 U/ml, p<0.001, and 87 vs 20, p<0.001, respectively) and 12 months (6.1 U/ml vs 3.0 U/ml, p<0.001, and 81.3 vs 20.2, p<0.001, respectively). No differences in post immunisation reaction rates were noted between the two vaccinated groups. This study demonstrated the safety and enhanced immunogenicity of the candidate meningococcal conjugate vaccine as compared with the licensed polysaccharide vaccine in adolescents.