Because of the presence of inequality of the effect of volatile anesthetics on various neurotransmission systems, a specific receptor is proposed. Nonetheless, the differences are only of the magnitude, and almost all synapses are equally affected. The outstanding features of the action of volatile anesthetics are this wide range of the target, and the steep dose-response curve. The steep dose-response curve indicates that various synapses respond to anesthetics with high cooperativity. When a string of amino acids folds into biologically meaningful structure by enclosing hydrophobic areas inside, some hydrophobic parts are left at the protein-water interface. These hydrophobic patches become the binding site for anesthetics. Because of the wide difference in the structures of anesthetics, it is difficult to assume a specific binding site of lock-and-key type for all anesthetics with all synaptic proteins. Presumably volatile anesthetics bind most hydrophobic patches nonselectively. The affinity to each patch may differ, and the relative specificity to each synapse may ensue. To define these areas as a receptor is a matter of opinion.