The prevalence of hepatitis B virus (HBV) markers was assessed in 1,841/2,178 (84.5%) dialysis patients (DP) cared for in 38/47 dialysis units (80.9%) in Latium. Among DP, 205 (11.1%) were HBsAg positive: 13.8% of males and 7.1% of females (p < 0.001); the prevalence increased with the length of time on dialysis (p for trend < 0.001). No differences in HBV (HBsAg and/or anti-HBc) distribution were seen related to age and sex. Of 664/1,539 vaccinated DP, 150 (22.6%) were anti-HBc positive and 239 (36.0%) positive for anti-HBs alone. Of 875/ 1,539 nonvaccinated patients, 146 (16.7%) had no HBV marker. Vaccination against HBV did not influence the diffusion of HBV in our dialysis units and must be coupled with the implementation of long-standing infection control strategies.