A comprehensive overview in the field of heterogeneously catalysed hydrogenations over gold surfaces and supported gold catalysts is given. It is also highlighted where the latter are superior to other hydrogenation catalysts. Basic principles including the adsorption and activation of hydrogen, structure-sensitivity, real structure of supported gold catalysts and attempts to identify the active sites are discussed. In reactions exhibiting a selectivity problem, e.g. hydrogenation of two C=C bonds or C=C versus C=O groups, the characteristic feature of gold catalysts is the preferred hydrogenation of one of these groups leading to monoenes, unsaturated alcohols and unsaturated ketones as reaction products important to the chemical industry. (c) 2005 Elsevier B.V. All rights reserved.