A case of hepatitis B virus reactivation leading to the diagnosis of a T cell lymphoma is reported. A 66-year-old woman with a past history (10 years before) of spontaneously recovered acute hepatitis B (with disappearance of serum hepatitis B surface antigen and appearance of anti-HBs), has been referred for hepatologic consultation for acute hepatitis. The patient was found positive again for hepatitis B surface antigen as well HBeAg and hepatitis B virus DNA. No other cause of liver disease was identified and a diagnosis of spontaneous hepatitis B virus reactivation was made. Five months later a peripheral T cell lymphoma was diagnosed. This unusual case confirms that natural immunity is not protective against hepatitis B virus reactivation and shows that such hepatitis B virus reactivation may precede the usual clinical manifestations of a peripheral T cell lymphoma.