The objective of this study was to evaluate the role of hepatitis B virus (HBV) precore mutations in patients with anti-HBe—positive chronic hepatitis B with or without previous known HBe antigen (HBeAg) viremic phase, and to assess the potential implication of precore mutants in HBeAg—negative reactivation after loss of HBeAg. Nineteen patients were studied: 7 had a previous HBeAg-positive phase and had spontaneous or therapeutically induced loss of HBeAg (group A); 12 had no previous HBeAg-positive phase (group B). Direct sequencing of PCR products was performed on serum collected during the anti-HBe—positive phase in the two groups. In group A, precore sequencing showed that 5 patients were infected by wild-type virus, 1 patient was infected with a precore mutant, and 1 patient was found to be infected by a mixture of wild-type and precore mutant viruses. In group B, precore sequencing showed that only 1 patient was infected with wild-type virus and that 11 were infected with precore mutants. In a few patients, the presence of HBeAg within immune complexes may explain HBeAg negativity. In conclusion, our results show that, in patients with anti-HBe—positive chronic hepatitis B: (1) precore mutations creating a stop codon are more frequently found in those without known previous HBeAg positivity; (2) after loss of HBeAg, the patients who have anti-HBe—positive reactivation are infected by wild-type virus, which suggests that reactivation is not related to precore mutations; (3) HBeAg negativity may be caused by immune complexes formation.