The immune response after hepatitis B (HB) vaccine HEVAC B was studied in 33 children (mean age 10 +/- 4 years) with advanced renal failure. Responders and protected patients were defined by antibody titres to HB surface antigen (anti-HBs) of greater than 10 and 50 mIU/ml, respectively. All received the initial recommended three injections at monthly intervals, and 23 received a booster injection (IB) 11 +/- 1 months after the third injection (I3). Loss of protection after I3 led to additional injections in 8 patients (25%). Vaccine was well tolerated and no HB infection occurred during the follow-up period (19 +/- 10 months). The percentage of responders was 91% 2 +/- 1 months after I3, and 100% 1 month, 13 +/- 1 months and 26 +/- 2 months after IB. The percentages of protected patients at these dates were 91%, 95%, 100% and 100%. Anti-HBs titres 1-3 months after I3 were useful for indicating those patients likely to have a rapid decline in anti-HBs titres, thus requiring serial anti-HBs determinations and additional injections to prevent a loss of protection. We conclude that at the expense of a reinforced vaccination schedule in 25% of patients, HEV AC B vaccine can safely achieve a sustained protection in more than 90% of uraemic children.