The response to vaccination with recombinant hepatitis B virus (HBV) vaccine is poor in haemodialysis patients. A defect in the antigen-presenting cells may be responsible for this hyporesponsiveness. To overcome this and to improve the response to HBV vaccine in dialysis patients, we used granulocyte-macrophage colony-stimulating factor (GM-CSF) as a vaccine adjuvant. Fifteen consecutive patients with chronic renal failure (CRF), commenced on dialysis, were stratified to receive either 40microg HBV vaccine (Engerix-B) at 0, 1, 2 and 6 months (group A, n=9) or 3microg kg-1 GM-CSF (Leucomax) on day 1 followed by the vaccination schedule described above (group B, n=6). All patients were negative for hepatitis B surface antigen (HBsAg), antibodies to hepatitis C virus (anti-HCV) and human immunodeficiency virus (HIV) serology. Titres of antibody to HBsAg (HBsAb) were quantitatively assayed, using enzyme-linked immunosorbent assay (ELISA), at 1, 2, 6 and 7 months from the first dose of vaccination. Only 44% of the patients in group A developed protective antibody levels (mean HBsAb: 22 IU l-1) Fifty per cent of responders developed protective antibody levels (HBsAb >10 IU l-1) only after the fourth dose of vaccination. In contrast, all six patients (100%) in group B developed protective levels of HBsAb (mean HBsAb: 70 IU l-1) (P<0.02). Sixty-seven per cent of the responders were protected after only the second dose of vaccination (P=0.046). No serious adverse effects of GM-CSF were observed in group B. Hence, haemodialysis patients respond poorly to HBV vaccine. GM-CSF is a safe vaccine adjuvant capable of stimulating an earlier and a stronger antibody response to HBV vaccine in haemodialysis patients.