Hepatitis B virus (HBV) reactivation is defined as the increase in viremia (> 1 log10 IU / ml) in a known patient with chronic or HBV–resolved infection. Since covalently closed circular deoxyribonucleic acid (cccDNA) is not removed from the hepatocytes, any event affecting the immune status promotes viral reactivation, sometimes severe or even fatal. We report an observation of an immunodeficient patient in whom viral B reactivation occurred one year after renal transplantation