The aim of the present study was: (a) to assess the effect of HBsAg on the survival of both renal grafts and patients, and (b) to determine the outcome of HBV chronic infection after renal transplantation. Fourteen patients seropositive for HBsAg but asymptomatic before renal transplantation (group A) were included in the study. The results were compared to those of 14 transplanted patients (group B) seronegative for HBsAg with similar age and immunosuppressive treatment. Four patients received a graft from a living-related donor and 10 patients from a cadaver donor in each group. Eight of 14 patients of group A showed, after renal transplantation, chronic hepatitis, which was not observed in any of the group B patients (p < 0.01). The rate of acute rejection episodes was significantly greater (p < 0.05) in group B than in group A. The graft survival was found to be similar in both groups at the 1st year, but significantly less (p < 0.01) in group B than in group A at the 5th year after transplantation. The survival of patients was found to be significantly less in group A than in group B at the 1st (p < 0.05) and 5th years (p < 0.01) after transplantation. In 2 patients of group A and 1 of group B anti-HCV was found, while HDAg plus anti-HD was found in 1 patient of group B. The HBV-DNA was found in 4 of 8 alive patients of group A.(ABSTRACT TRUNCATED AT 250 WORDS)