Chronic hepatitis B virus (HBV) infection was revealed by a severe acute hepatitis with positive HBsAg in a patient. The positivity of IgM anti-HBc antibody, the rapid negativization of DNA-HBV, the early normalization of liver function tests and the exclusion of other causes of acute hepatitis favored the diagnosis of recent HBV infection and were predictive of a rapidly favorable outcome. However, immunohistochemical study of a transjugular hepatic biopsy sample discovered HBsAg within the liver, with a characteristic topographic distribution of chronic HBV infection. The patient's evolution confirmed this diagnosis, because 20 months later he had chronic active hepatitis with persistent replicative activity of HBV. This case illustrates the heterogeneity of HBV infections, emphasizing the need of an accurate diagnosis and a careful follow up until the complete resolution of each case of acute hepatitis with positive HBsAg.