We describe a case of postoperative subdural dislocation (between dura and arachnoidea spinalis) of an epidural catheter. After 24 h of normal functioning of the catheter, the injection of 5 ml lidocaine caused an extensive unilateral sensory block including the cranial nerves. X-ray control excluded an epidural or intrathecal position of the catheter. A delayed dislocation of the epidural catheter into the subdural space can occur but this complication only usually becomes evident after injection of a normal dose of local anaesthetic into the catheter and can have catastrophic consequences. The safety of patients can only be guaranteed if epidural catheters are managed solely by professional anaesthesiological personnel. Anatomy, mechanisms of complications and clinical differential diagnosis are discussed.