A stop codon in the precore genome of the hepatitis B virus (HBV) in anti-HBe positive HBV carriers may be associated with a more progressive form of HBV infection. Earlier studies, however, were mainly performed in patients from the Mediterranean area who had severe infection. The aim of this study was to evaluate the prevalence of precore mutants in an unselected population living in northern Europe. Twenty of 42 of these patients are infected predominantly with a virus strain, which has the typical stop codon in the precore genome, characterised by a mutation at base 83. In six patients there was an additional G to A mutation at base 86 of the precore genome. Statistical analysis showed no difference between the patients with or without a stop codon in the precore genome. When patients with a double mutation at base 83 and 86 of the precore genome were compared with the other anti-HBe positive HBV carriers, however, the corresponding clinical data were worse. Therefore we suggest, that it is not the stop codon in the precore gene itself, but the occurrence of a double mutation at bases 83 and 86, which is associated with a more severe course of disease in anti-HBe positive HBV carriers.