In view of the present world-wide diffusion of HIV, we evaluated the possible presence of persons infected by HIV or suffering from AIDS among the patients and staff of two Dialysis Centers. In the past these centers have been found to be at a high risk for HBV infection. The results of this seroepidemiological study, though rather reassuring for the time being, have led the authors to propose specific prevention rules, owing to the nature of activities in these medical structures and in light of the fact that the presence of HIV is beginning to be reported in other such centers.