This text for R&D workers in inorganic, bioinorganic, physical, organic and clinical chemistry describes how macrocyclic ligands containing oxygen, nitrogen, phosophorus, sulphur and arsenic donors can be prepared, in addition to ligands with mixed donor sets. It also shows how variations in ring size, degress of unsaturation, subsituents within the ring and pedant donor groups can lead to interesting and novel properties; and also how macrocyles provide a novel way of mimicing the binuclear metal sites found in many enzymes, so leading to applications of macrocyles in such areas as new solvent extractants for metal ions, new catalysts and new materials for electronic devices.