Abstract: A compact, multi-stage, co- or counter-current liquid-liquid extraction apparatus includes first and second mixer-settlers which share a common wall. Each of the first and second mixer-settlers comprises a mixing chamber having an agitator mounted therein, upper and lower settling chambers, and upper and lower baffles between the mixing chamber and the upper and lower settling chambers respectively. The liquid media to be contacted in each mixer-settler are supplied to the mixing chamber from which dispersion flows upwardly and downwardly into the upper and lower baffles. Disengaged lighter medium flows out from the upper settling chamber to the mixer-settler, over a weir whose length exceeds half the length of the common wall, while disengaged heavier medium flows out of the lower settling chamber of one mixer-settler to the corresponding mixing chamber of the next mixer-settler. In one form the disengaged heavier medium also overflows a corresponding outlet weir to pass on to the next mixer-settler.