The histological features in liver biopsy specimens from seven patients with acute exacerbation of chronic type B hepatitis were analysed. In all the cases typical changes of acute hepatitis were superimposed on signs of chronicity, namely peripheral piecemeal necrosis, plasma cell infiltration and porto-portal bridges, which in three cases contained elastic fibres. Reactivation of silent hepatitis B virus chronic infection should be considered as a possible diagnosis in any patient with histological findings of acute and chronic hepatitis.