Twenty-one children and adolescent patients, 2-19 years of age, on renal replacement therapy were immunised at monthly intervals with three doses of 20 micrograms hepatitis B vaccine (Heptavax B, Merck Sharp & Dohme). In the absence of seroconversion, vaccination was continued with monthly doses of 40 micrograms hepatitis B vaccine until antibody to hepatitis B surface antigen became positive. The rate of seroconversion increased from 33.3% (7 of 21) to 76.1% (16 of 21) and 85.6% (18 of 21) with three, four and five vaccine injections respectively. Three patients had no immune response despite six to seven vaccine dosages; they had previously received immunosuppressive therapy. Antibody titres measured 1 year after seroconversion were found to be within the protective range (85-2500 mIU/ml). These results show that the impaired immune response to hepatitis B vaccination in young dialysis patients can be overcome by increasing the number of injections and the dose of the vaccine. Protective antibody titres are maintained for at least 1 year after vaccination. Immunosuppressive therapy may interfere with the vaccine response.