A controlled, randomized trial was conducted in urban areas of Karachi and Lahore with the aim to look for ways to improve the cost-effectiveness of hepatitis B vaccination. Children under 15 years old (including neonates) were selected and screened for immunization by three regimens according to the frequency and doses of the recombinant vaccine used (Heberbiovac HB, Heber Biotec, Havana). Group A received 10 microg at 0, 1 months; group B (control) received 10 microg at 0, 1 and 2 months (standard regime), and group C received 5 microg at 0, 1 and 2 months. Antibody levels were titrated 2 months after the last dose. Cut-off for seroprotection and hyperresponse were taken as 10 and 100 IU/L, respectively. Nine hundred and ninety children were included and evaluated after discarding those positive for serological hepatitis virus infection markers. Seroprotection rates were 100, 99.7 and 99.7%, and hyperresponse was achieved by 92.7, 99.4, and 97% of the vaccinees in groups A, B, and C, respectively. The same good result was obtained in extreme ages subgroups (< or =1 year and > or =10 years old). The 1-year follow up of the children from Karachi showed good persistence of seroprotection (98, 100, and 99.4%) and hyperresponse (79.7, 96.7, and 87.4%). It is concluded that it is feasible to improve the cost-benefit ratio and compliance of hepatitis B vaccination by means of a two-shots or reduced dose schedule of the vaccine employed in the trial.