Solvent extraction columns equipped with reciprocating plates are discussed. It is shown that reciprocating-plate columns with two sets of plates, alternately mounted on separate rods, and with a phase shift of 180 deg between the motion of the two rods, are, from a mechanical standpoint much superior to previously proposed types: under practical operating conditions, the periodic variation of the base pressure is only a small fraction of the static head. Mass transfer experiments with the system tributyl phosphate in keroseneacidic aqueous solutions of uranyl nitrate show that both high specific throughputs and reasonably good efficiencies can be attained in this type of column. The results of a comparison with mixer-settlers and pulsed columns indicate the potential of the reciprocating-plate column in hydrometallurgical applications in which the requirements on separation efficiency are moderate, but the scale of the operation is large.