The reactogenicity and safety of an experimental hepatitis B (HB) vaccine containing adjuvant system (AS04) was compared with a licensed vaccine in a phase III, single-blind, randomised study in healthy volunteers >or=15 years of age. A total of 1303 subjects were enrolled to receive either two doses of HB-AS04 (0, 6 months) or three doses of the comparator vaccine (0, 1, 6 months). Two doses of HB-AS04 elicited seroprotection rates close to 100% and two-fold higher GMTs than the comparator vaccine. Results showed that both vaccines were well tolerated and the general safety profile of HB-AS04 was similar to that of the comparator vaccine.