Patients on maintenance hemodialysis (HD) have poor seroconversion rate after hepatitis B vaccination. The present study was designed to test the efficacy of granulocyte-macrophage colony-stimulating factor (GM-CSF) as an adjuvant to hepatitis B vaccination for improving seroconversion rate in maintenance HD patients. Twelve chronic HD patients were randomly assigned to receive either hepatitis B vaccination alone or hepatitis B vaccination 24 h after 1 dose of GM-CSF for primary immunization. A group of 16 chronic HD patients who had not seroconverted after a standard two-dose hepatitis B vaccination were randomly assigned either to a booster dose of hepatitis B vaccine alone or a booster dose given 24 h after one dose of GM-CSF. In the primary immunization group only 2 of 6 patients (33%) who had received vaccination alone, versus 5 of 6 patients (83%) who had received hepatitis B vaccine after one dose of GM-CSF, developed seroprotective antibody titers. Moreover, seroprotective antibody titers (IU/ml) were significantly higher in the latter group (275 ± 286.5 vs. 14 ± 22, p < 0.05). In patients who had not seroconverted with prior hepatitis B vaccination, GM-CSF adjuvant therapy significantly increased the seroconversion rate versus booster dose alone (87.5 vs. 25%, respectively, p < 0.02), with significantly higher seroprotective antibody titers (84 ± 80 vs. 19 ± 33 IU/ml, respectively, p < 0.05). These findings suggest that administration of one dose of GM-CSF, as adjuvant therapy, prior to primary or booster dose hepatitis B vaccination may significantly increase seroconversion rate and seroprotective antibody titers in chronic HD patients.