Diminished antibody responses to the dosage of hepatitis B (HB) vaccine indicated for healthy adults has led to a greater dosage recommendation (40 microg of HB surface antigen [HBsAg]) for adults with chronic renal failure (CRF), but an appropriate dosage for children with CRF has not been established. Seventy-eight children and adolescents with CRF (22 patients, predialysis; 42 patients, chronic dialysis therapy; 14 renal transplant recipients) aged 1 to 19 years (mean, 10.1 years) were enrolled onto a study to test a three 20-microg dose course of the HB vaccine Recombivax HB (Merck & Co, Inc, West Point, PA). The vaccine was well tolerated; no patient had a serious adverse event attributable to vaccine, and no patient withdrew from the study because of an adverse event. Overall, 91% of 66 patients administered three doses had a protective titer of 10 mIU/mL or greater for antibody against HBsAg (anti-HBs) and a geometric mean titer (GMT) of 733 mIU/mL, with seroprotection rates and GMTs among predialysis, dialysis, and renal transplant patients of 100% (4,140 mIU/mL), 94% (419 mIU/mL), and 64% (152 mIU/mL), respectively. All (100%) predialysis patients had a 10-mIU/mL or greater anti-HBs titer after only two doses of vaccine compared with 64% of dialysis patients and 50% of transplant recipients. Eighty-eight percent of 57 fully vaccinated patients tested 12 months after the first dose retained a 10-mIU/mL or greater anti-HBs titer. A regimen of three 20-microg doses of Recombivax HB is suitably immunogenic for children with CRF not administered immunosuppressive medication. When possible, at least two, and preferably all three, doses of vaccine should be administered before progression to end-stage renal disease. Copyright 2002 by the National Kidney Foundation, Inc.