1. In view of the large number of possible molecular targets of general anaesthetics, it is necessary to have some criteria for judging which targets are important for producing general anaesthesia and which are probably not. 2. We consider in detail two criteria: sensitivity to clinically relevant concentrations of anaesthetics and stereoselectivity to anaesthetic optical isomers. 3. The targets which currently emerge as most important belong to an anaesthetic-sensitive superfamily of genetically related fast neurotransmitter-gated receptor channels present at central synapses.