Anaesthetic drugs are mostly inhaled anaesthetics and intravenous anaesthetics. Inhaled anaesthetics include one gas such as nitrous oxide and several volatile anaesthetics like halothane, enflurane, isoflurane, desflurane etc. Of the intravenous anaesthetics, thiopentone, propofol, midazolam, etomidate, ketamine etc. are most commonly used. The pharmacologic effects of the anaesthetics particularly on circulation and ventilation must be appreciated before use. This chapter also reviews the pharmacological effects of common muscle relaxants in use.