Objective To compare seroconversion using hepatitis B vaccine between hemodialysis (HD) and peritoneal dialysis (PD) patients. Design Data on PD patients vaccinated were collected retrospectively for the period 1992 to 1995. The data on HD patients were collected prospectively from 1991 to 1994. Setting A university outpatient dialysis center. Participants All adult patients who received all four doses of hepatitis B vaccine while on dialysis were included (47 PD and 50 HD patients). Intervention Recombinant hepatitis B vaccine (Engerix), 40 μg IM was administered at 0, 1, 2, and 6 months. Main Outcome Measure Seroconversion was measured after completion of the vaccination series. Results 74% of the HD patients seroconverted compared to 53 % of PD patients (p = 0.03). Older, heavier patients compared to all the other patients had a lower seroconversion rate in both the HD patients (55 % vs. 78 %) and PD patients (38 % vs. 59 %) (p = 0.03). Conclusion The seroconversion rate to recombinant hepatitis B vaccine is lower in patients on PD than on HD for unclear reasons. Further studies are required to determine the etiology of this difference.