A survey of the recent literature on gas-liquid reactors stirred by dual impellers shows that the combination of two Rushton turbines is most probably the best one for general purposes. Nevertheless, for specific utilizations in which high shear should be avoided or only part of the main parameters is of relevant importance, combinations making use of one (hybrid configurations) or two axial or mixed flow impellers can be competitive. The report aims at presenting the state-of-the-art, examining the advantages and drawbacks of the more investigated combinations in order to provide a guide for applications and future research work.