AgHBs incidence in various population groups from the Iassy region was relatively high in 1991, ranging from 3.8% in blood donors to 75.0% in patients with severe acute virus hepatitis. As compared to the incidence values recorded in 1973, 18 years ago, in the population of the same territory, some mutations were observed, the most important being the more then threefold reduction of the AgHBs incidence in blood donors. In subjects with liver diseases and in risk groups, the frequency of AgHBs carriers maintains at a high level.