This paper describes a case of drug-induced hepatitis that onset in a patient who was hospitalised in our department after administration of calcium heparin. The rarity of the case was shown not only by the very short time elapsed between cause (drug administration) and effect (bio-humoral changes detected), but also by the histology results of the liver biopsy. This latter confirmed that mechanisms of idiosyncrasy, which may cause liver cell necrosis, can occur after administration of any drug.