Substance abuse remains one of the biggest social problems around the world. Anaesthesiologists should be aware of this problem and the most likely effects and potential risks associated with the abuse of illicit substances. Some of these patients may present at preanaesthetic clinic as well as in emergency situations including intensive care unit. Use of illicit drugs encourages reckless driving and thus increases the potential for motor-vehicle accidents and suicide attempts, often requiring anaesthesia for emergency and trauma situations. Anaesthesia and postoperative analgesia in patients dependent on psychoactive substances poses special problems.