The case of a patient under tibolone therapy for two years who developed a mixed-type liver injury with prolonged cholestasis and features of the vanishing bile duct syndrome following a ten weeks treatment with St. John wort (Hypericum Perforatum) infusions is reported. In the absence of evidence of a potential role for concomitant medication i.e. hydroxychloroquine sulfate to play a role in the clinical, biochemical and morphological picture, an interaction between the herbal preparation and tibolone was suspected as the likely cause of liver damage.