24 Chinese children aged 1.5-5 years and positive for hepatitis B surface antigen (HBsAg), hepatitis B e antigen (HBeAg), hepatitis B virus DNA polymerase (HBV DNAp), and HBV DNA on at least three occasions in the 6 months before the trial were randomised to receive either vitamin B complex or intramuscular recombinant alpha 2-interferon (r-IFN) ('Roferon') 10 X 10(6) IU/m2 thrice weekly for 12 weeks. In all 12 subjects receiving r-IFN, HBV DNAp and HBV DNA levels fell during the course of r-IFN injections. Within 4 weeks of cessation of r-IFN injection, the HBV DNAp and HBV DNA returned to pre-trial levels except in 2 subjects, in whom loss of HBV DNAp and HBV DNA was sustained for up to 18 months from onset of the trial. 1 child lost HBeAg at 18 months. 2 of the 12 children in the placebo group also had a sustained loss of HBV DNAp and HBV DNA during the 18 months, with 1 child losing HBeAg at 18 months. All 24 subjects remained positive for HBsAg. r-IFN produced very slight side-effects except for pyrexia and the "flu" syndrome, both of which showed rapid tachyphylaxis. In the dose given r-IFN was safe but had no long-term beneficial effects on HBsAg carriage in Chinese children.